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A 

HANDBOOK 


INCANDESCENT  LAMP 
ILLUMINATION 

1913 


COPYRIGHT 

by  the 
GENERAL  ELECTRIC  CO 


PRICE    FIFTY    CENTS 


Y-177 


Mazda  Lamps  For  Standard 
Lighting  Service 

100-130  Volts 
Straight  side  bulbs 

15,  20,  25,  40,  60, 100,  150,  and  250  watts. 
Round  bulbs 

15,  25,  40,  60,  100,  150,  400,  and  500  watts, 

200-260  Volts 
Straight  side  bulbs 

25,  40,  60,  100,  150,  and  250  watts. 
Round  bulbs 

25,  40,  60,  100  and  500  watts. 

(For  complete  schedule  of  Mazda  lamps,  see 
page?;  66  and  66) 


PREFACE 


In  preparing  this  book  the  object  has  been 
to  provide  a  ready  reference  for  those  inter- 
ested in  incandescent  lamps  and  in  problems 
dealing  with  incandescent  lamp  illumination. 
With  this  in  view  there  have  been  included 
tables  and  formulae  covering  the  various 
problems  that  may  present  themselves  to 
the  central  station  man,  to  the  lamp  solicitor, 
to  the  student,  and  to  the  user  of  incandes- 
cent lamps. 

As  this  is  the  first  publication  of  this  nature, 
it  is  to  be  expected  that  some  sections  will 
contain  superfluous  matter,  while  others  will 
not  be  covered  thoroughly  enough  to  meet 
the  requirements  as  intended.  Suggestions, 
criticisms  and  corrections  from  those  who  find 
use  for  this  book  are  earnestly  solicited,  as 
such  will  help  materially  in  the  preparation 
of  future  editions. 


268686 


CONTENTS 


Dictionary  of  Terms 
General  Formulae 

Photometers  and  Photometer  Methods 
Candle-power  Relations 

Illumination  Calculations 
Point  by  Point  Method 
Flux  of  Light  Method 

Reflectors 

Classes  of  Lighting  Service 
Miniature  Lamps 
Sign  Lighting 
Street  Lighting 
Mill  Lighting 

General  Information  on  Incandescent  Lamps 
History  of  the  Incandescent  Lamp 
Ktching  and  Frosting 
The  Best  Lamp 
Cleaning  and  Handling  of  Incandescent 

Lamps 
Cost  of  Light 

Characteristics  of  Lamp  Filaments 
Average  Performance  of  Lamp  Filaments 
Energy  Losses  in  Lamp  Filament 
Prevention  of  Static  Effects 

Distribution  Systems 
Formulae 
Wire  Tables 
Rectifier 
Watt-hour  Meters 

Extracts  from  N.  E.  C. 
Storage  Batteries 

Transformers 
Types 

Connections 
Testing 

Miscellany 

Trignometric  Functions 
Mensuration 

Rates 

Resuscitation  from  Electric  Shock 

Index 


Dictionary  of  Yeriris 


The  Actual  Life  of  a  lamp  is  the  number  of 
hours  it  burns  before  its  filament  breaks,  or  be- 
fore it  becomes  useless. 

Ampere.  The  unit  of  electric  current  strength 
is  the  ampere.  It  is  that  current  which,  when 
passed  through  a  solution  of  silver  nitrate  in  a 
silver  voltameter,  will  deposit  silver  at  the  rate 
of  .001118  grams  per  second.  It  is  the  amount  of 
current  flowing  through  a  resistance  of  one  ohm 
under  a  pressure  of  one  volt. 

Candle=Power  is  the  unit  of  intensity  of  light 
emitted  from  a  lamp  or  other  light  source.  (See 
"Candle-Power  Relations"  for  further  discus- 
sion) . 

The  Cold  Resistance  of  a  filament  is  its  resist- 
ance at  0°  centigrade. 

Efficiency  as  applied  to  incandescent  lamps  is 
usually  expressed  in  watts  per  candle.  (See 
"Candle- Power  Relations.'') 

Fechner's  Fraction  is  the  minimum  fractional 
difference  between  any  two  luminosities  which 
the  eye  can  perceive.  This  ability  to  discern 
difference  in  luminosities  depends  on  the  ca- 
pacity of  the  eye  to  determine  shade  perception. 
The  value  of  this  fraction  attains  its  normal 
value,  that  is,  the  eye  is  at  its  full  sensitiveness 
when  the  illumination  is  about  1  foot-candle. 
(See  page  83.) 

The  Flux  Factor  or  lumen  constant  for  any 
given  zone  is  the  constant  which  multiplied  by 
the  average  candle-power  in  that  zone  gives  the 
total  quantity  of  light  expressed  in  the  lumens 
emitted  in  that  zone. 

Glare  is  a  condition  of  brilliancy  of  light  sources 
or  illuminated  surfaces,  whereby  ocular  discom- 
fort or  interference  with  vision  results.  Glare  is 
likely  to  occur  when  a  bright  light  or  excessive 
contrast  of  intensity  intrudes  in  the  field  of 
vision. 

Illumination,  as  generally  used  in  a  technical 
sense,  refers  to  luminous  radiation  falling  on 
surfaces  in  contradistinction  to  the  light  emitted 
from  a  lamp. 

Intensity  of  Illumination  is  measured  in  foot- 
candles,  one  foot-candle  being  the  intensity  in- 
cident at  right  angles  upon  a  plane  one  foot 
distant  from  a  point  source  of  one  candle-power. 

Flux  of  Illumination  is  measured  in  lumens 
and  is  equal  to  the  intensity  of  the  illumination 
multiplied  by  the  area  over  which  it  is  dis- 
tributed, i.  e.,  lumens  =  foot-candles  X  square 
feet. 

Intrinsic  Brilliancy,  or  surface  brilliancy,  is  the 
intensity  of  light  emitted  from  a  source  per  unit 
of  its  projected  area.  It  is  usually  expressed  in 
candle-power  per  square  inch. 

1 


Kelvin's  Law.  The'most  economical  area  of  a 
conductor  is  that  for  which  ^the  annual  cost  of 
energy  wasted  is  equal  to  the  anriual  interest  on 
that  portion  o?  the  capital  outlay  which  repre- 
sents the  cost  of  metal  used.  (See  example 
page  100.) 

The  Kilowatt  is  1000  watts. 

Lumen.     (See  '  Candle-Power  Relations.") 

Luminous  Efficiency  denotes  the  ratio  of  the 
luminous  radiation  of  an  illuminant  to  its  total 
radiation. 

The  Mean  Horizontal  Candle=Power  is  the  aver- 
age of  the  candle-powers  in  the  horizontal  plane 
in  all  directions  about  a  lamp  whose  axis  is  ver- 
tical. 

The  Mean  Spherical  Candle=Power  is  the  mean 
of  the  candle-powers  in  all  directions  about  a 
lamp. 

Mean  Zonular  Candle-Power  is  the  average 
candle-power  given  off  in  the  particular  zone  in 
question. 

The  Micron  is  the  unit  of  light  wave  length 
and  is  equal  to  .001  mm. 

A  Mil  is  .001  inches. 

A  Circular  Mil  is  the  area  of  a  circle  1  mil  in 
diameter.  The  area  of  any  conductor  in  circular 
mils  is  equal  to  the  square  of  its  diameter  in 
mils,  or  to  1,000.000  times  the  square  of  its  di- 
ameter in  inches.  1  sq.  mil  is  equal  to  1.273 
times  one  circular  mil 

The  Net  Efficiency  of  an  illuminant  is  the  ratio 
of  the  luminous  energy  to  the  total  energy  con- 
sumed. 

Ohm.  The  unit  of  resistance  is  the  ohm  and 
is  the  resistance  that  would  be  offered  to  the 
flow  of  an  electric  current  by  a  column  of  mer- 
cury 106.3  cm.  in  length,  and  14.4521  grams  in 
mass. 

A  Photometer  is  a  device  used  to  compare  the 
candle-powers  of  light  sources.  The  simple  pho- 
tometer consists  of  two  lamp  receptacles,  one  at 
either  end  of  a  scale  called  the  photometer  bar. 
Between  these  receptacles  is  a  movable  sight  box 
for  comparing  the  light  intensities  incident  on 
the  screen  contnined  therein. 

Purkinje  Effect.  If  a  red  field  and  a  blue  neld 
are  illuminated  so  as  to  appear  of  about  the 
same  brightness,  and  then  the  intensity  of  illu- 
mination on  both  be  greatly  reduced  in  the  same 
proportion,  the  red  field  will  appear  darker  than 
the  blue;  and  conversely,  if  the  intensity  be 
greatly  increased  the  red  will  appear  brighter. 

Selective  Radiation  occurs  where  a  surface 
emits  radiation  of  the  various  wave  lengths  in 
different  proportions  from  that  of  a  theoretically 
black  body  at  the  same  temperature. 

The  Spherical  Reduction  Factor  is  the  ratio  of 
the  mean  spherical  candle-power  to  the  mean 
horizontal  candle-power. 


Temperature  Coefficient.  The  resistance  of  a 
filament  changes  by  the  addition  '  or  subtraction) 
of  a  certain  percentage  of  the  cold  resistance  for 
each  degree  of  temperature  change.  This  per- 
centage is  called  the  temperature  coefficient. 
The  formula  for  finding  the  resistance  at  any 
temperature  is 

Rt  =  Ro  +  Ro  a  t 

where  Ro  =  the  cold  resistance 

a  =  the  temperature  coefficient 
t  —  the  degrees  centigrade  at  which 
Rt  is  to  be  found. 

The  Useful  Life  of  a  lamp  is  the  number  of 
hours  it  burns  before  it  drops  to  80%  of  its  initial 
candle-power. 

The  Visible  Spectrum  includes  wave  lengths 
varying  from  approximately  0.4  microns  to  0.8 
microns. 

Visual  Acuity  is  the  ability  to  observe  detail. 
Acuity  is  measured  by  the  ratio  of  the  distance 
at  which  the  eye  can  discern  the  details  of  a 
standard  letter  to  the  distance  regarded  as 
standard  for  that  letter.  (See  article,  page  83.) 

The  Volt  is  the  unit  of  electro-motive  force  or 
electrical  pressure.  It  is  the  pressure  necessary 
to  force  a  current  of  one  ampere  through  a  re- 
sistance of  one  ohm. 

The  Watt  is  the  unit  of  electrical  power;  it  is 
the  product  of  instantaneous  values  of  electro- 
motive force  and  current  in  the  circuit  when 
their  values  are  respectively  one  volt  and  one 
ampere. 

The  Watt-Hour  is  the  unit  of  electrical  energy, 
and  is  the  product  of  power  and  time. 


Formulas 

OHM'S  LAW  FOR  DIRECT  CURRENT 

E  =  IR 

Volts  =:  amperes  X  ohms 
Amperes  —  volts  -f-  ohms 
Ohms  —  volts  -7-  amperes 

Series  Circuit 

R  =  n  +  r2  +  rn 

E  =  ei  +  62  +  en 

R  is  the  total  resistance  of  the  circuit 
and  is  the  sum  of  the  resistances  of  sections  of 
the  circuit. 

E  is  the  total  wattage  and  is  the  sum 
of  the  voltage  drops  across  the  resistances  r, 
r*  and  rn . 


Shunt  or  Multiple  Circuit 


I   =  ii  4-  ia  4-  is 

E  —  e  —  62  =  e« 
1 

R  = 


rsr3  ~^~ rira  +rirs 

Parallel  and  Series  Circuit 
I 


-AW/A    i  I     WWV 


Fig.  1 

I   :=  h  4-  ia  4-  is 

E  =  Ir  4-  e  4-  Ir4 

e  =  hn  =  isra  =  iara 

Power  in  Direct  Current  Circuits 

Watts  =  volts  X  amperes 
Amperes  =  watts  -f-  volts 

OHM'S  LAW  FOR  ALTERNATING  CURRENT 

E-IZ 

Volts  :=  amperes  X  impedance  ohms 
Z  =  impedance  ohms  =  \/Ra  +  X2 
R  =  ohms  resistance 
X  =  ohms  inductive  reactance 
The  voltage  drop  due  to  inductive  reactance 
is  90°  ahead  of  the  IR  drop  and  the  impedance 
drop  is  the  resultant  of  the  two.    When  repre- 
sented graphically  the  IZ  drop  is  the  diagonal  of 
the  parallelogram  constructed  on  the  IX  and  IR 
drops.     As  the  diagonal  is  equal  to  the  square 
root  of  the  sum  of  the  sides  squared, 


The  common  factor  I  cancels  out  so  that 
Z  =  VR2:f  X2 


Power  in  Alternating  Current  Circuit 

Watts  =  volts  X  amperes  X  power- factor 
The  power-factor  is  the  cosin  of  the  an- 
gle between  the  impedance  volts  IZ  and  the  volt- 
i> 

age  drop  IR  and  is  equal  to  — . 
/j 

Conversion  Factors 

(746  watts 

~  |  33 ,000  ft.  Ibs.  permin. 
f . 00134  h. p. 


1.44.24  ft.  Ibs.  per  min. 

|  .000000377  kw-hrs. 
~  \  .0000005     h.p.  hrs. 

f  1000  watt 
,  v  _  J  1-34  h.  p. 

]  2,655,400  ft.  Ibs.  per  hr. 

1229  Ibs.  of  coal  oxidized  per  hour 

flOOO  watt  hours 

I  1.34  horse-power  hrs. 
1  kw-hr.       -  •<  2,655,400  ft.  Ibs. 

229  Ibs.  of  coal  oxidized  with  per- 

L       feet  efficiency. 

(  .746  kw-hr. 
_  J  1.980,000  ft.  Ibs. 

]  172  Ibs.  of  coal  oxidized  with  per- 

L       feet  efficiency. 

Calculation  of  Lamp  Data 

Candle-power  —  watts  -r  watts  per  candle 
Candle-power  =  volts  X  amperes  ~r  watts  per 

candle 
Candle-power  =  ohms  X    (amperes)  2  ~-  watts 

per  candle 

Watts  =  candle-power  X  watts  per  candle 
Watts  per  candle  =.  watts  -r  candle-power 
Amperes  =  candle-power  X  w.p.c-  -r  volts 
Ohms  =  watts  ~r  (amperes)2  =  candle-power  X 

w.p.c.  -r  (amperes)2 
Volts  =  watts  -r  amperes  =  candle-power  X  w. 

p.c.  -r  amperes 
Mean  spher.  C.P.  =  mean    hor.    C.P.    X   mean 

spher.  C.P.  factor 

Mean  spher.  C.P. 
Mean  spher.  C.P.  factor  =   M        h       c.p. 

Mean    hor.    C.P.  =  j^^^f^^ 
Total  cost  of  lighting  (renewal  cost  and  cost  of 
power)  for  any  given  number  of  hours  H. 
is  equal  to 

f  H  X  Price  of  Lamps  )   ,  \  H  X  Initial  watts 
\  Total  life  >•      <  1000 

Cost  of  power  per  kw-hr.  | 


Method  of  Photometering  lncandes= 
cent  Lamps 

As  all  lamps  must  be  photometered  and  labeled 
with  the  voltage  at  which  they  give  the  required 
candle-power,  it  is  necessary  to  have  working 
standards  with  which  they  may  be  compared  in 
order  that  the  rating  be  uniform.  These  stand- 
ard lamps  are  carefully  selected  and  rated  on  an 
accurately  designed  precision  photometer,  and 
are  then  checked  by  the  Electrical  Testing- 
Laboratories. 

It  is  quite  possible  to  determine  when  the  two 
sides  of  a  screen  are  illuminated  to  the  same 
intensity,  when  some  arrangement  is  made 
whereby  both  sides  can  be  viewed  at  the  same 
time.  This,  combined  with  the  law  of  inverse 
squares,  forms  the  basis  of  all  photornetering 
methods.  A  working  standard,  made  as  ex- 
plained above,  is  set  in  a  revolving  holder  at  one 
end  of  a  photometer  bar,  and  the  voltage  is  ad- 
justed on  a  lamp  at  the  other  end,  known  as  the 
back  standard,  until  equal  intensities  are  ob- 
served on  the  screen.  If  it  is  desired  to  "set" 
this  back  standard  for  the  same  candle-power  as 
the  standard  lamp,  the  screen  must  be  halfway 
between  the  two  lamps,  that  is,  in  the  equation, 

'2  ,2 

—-  P"  *    =  —      the  ratio      —      must  be  unity. 

C.   P.  2  A2  d2 


C.P. 


C.P.o 


Fig.  2 


After  "setting"  the  back  standard,  the  work- 
ing standard  is  replaced  by  the  lamp  to  berated, 
and  the  voltage  is  adjusted  on  this  lamp  until  a 
"balance"  is  obtained  on  the  screen.  That  volt- 
age is  marked  on  it  as  the  voltage  at  which  it 
will  give  its  rated  candle-power.  With  a  little 
experience  the  operator  soon  becomes  an  ac- 
curate reader,  being  able  to  check  her  readings 
with  little  or  no  variation. 

Photometer   Heads 

The  types  of  photometers  in  most  general  use 
are  those  employing  the  Bunsen  and  the  Lumner 
Brodhun  sight  boxes  and  the  flicker  photometer. 


In  the  Bunsen  sight  box,  mirrors  are  arranged 
so  that  both  sides  of  a  screen  can  be  observed  at 
the  same  time.  The  screen  is  made  of  white 
opaque  paper  with  a  sharply  defined  translucent 
spot,  usually  made  with  paraffine,  in  the  center. 
The  Leeson  disc  is  a  slight  improvement  over 
the  Bunsen  screen.  This  consists  of  a  trans- 
lucent disc  between  two  opaque  discs  with  two 
star  shaped  apertures  opposite  each  other.  _  Al- 
though they  are  not  the  most  accurate  'sight 
boxes,  they  are  the  least  tiring  to  the  eyes  when 
used  continually. 


Fig.  3 

The  Lumner  Brodhun  Screen  is  a  far  more 
satisfactory  form  for  precise  work.  It  is  some- 
what intricate  as  will  be  seen  from  Fig.  3  which 
shows  the  sight  box  in  plan.  The  box  is  mounted 
on  the  photometer  bar  with  its  axis  of  rotation 


lUiii  UULII  siu.cn  uy    LUC  u^i\->  \JL   i.ii^  mil  ji  wi  o  t- 1,  A-  x 

nd  the  right  angled  prisms,  A,  Bt  shown  in  plan 


Fig.  4  Fig.  5 

as  shown.     When  the  prisms  are  cemented,  the 
spaces  between  the  strips  are  transparent,  but  at 


the  strips  there  is  a  total  reflection  for  light  enter- 
ing normal  to  the  free  prism  faces.  Therefore 
the  odd  numbered  rays  (Fig.  4)  received  from 
c  cf  via  F\  enter  the  sight  field  only  through  the 
cemented  faces,  and  the  even  rays  from  d  dr  via 
Fs  only  by  total  reflection  at  the  strips.  The 
arrows  in  the  figure  show  plainly  the  course  of 
the  rays.  The  result  is  a  field  resembling  Fig.  5. 
each  half  circle  receiving  light  from  one  side  of 
the  screen  and  having  superposed  upon  it  a 
trapezoidal  area  received  from  the  other  side  of 
the  screen.  These  areas  are  slightly  darkened  by 
absorption  from  the  glass  strips  me  and  gbt  so 
that  when  everything  is  in  balance  one  has  two 
equally  shaded  areas  in  a  uniform  field.  One 
can  work  either  by  uniformity  of  field  or  by 
equality  of  contrast  of  the  trapezoids,  preferably 
the  latter  particularly  in  comparing  lights  differ- 
ing slightly  in  color. 

When  lights  of  two  different  colors  are  to  be 
compared,  as  for  instance  red  and  blue,  it  is  ex- 
tremely difficult  to  judge  when  the  intensities 
are  equal.  For  precise  work  the  flicker  photo- 
meter is  used.  In  this  type  a  screen  is  illuminated 
by  the  two  sources  of  light  in  rapid  alternation. 
When  the  speed  is  adjusted  between  10  and  20 
alternations  per  second  the  illumination  appears 
to  flicker  until  the  intensities  of  the  two  become 
equal,  or  the  flash  from  one  bridges  over  the 
gap  to  the  flash  from  the  other. 

The  Sharp  Millar  Illuminometer  is  used  quite 
extensively  as  a  portable  instrument.  A  com- 
partment at  one  end  of  the  blackened  interior 
contains  a  Lumner  Brodhun  prism.  At  this  end 
of  the  box  is  an  elbow  tube,  the  top  of  which  is 
fitted  with  a  diffusing  cap  of  milk  glass.  A  mirror 
is  placed  at  the  elbow  of  the  tube  which  reflects 
the  light  rays  to  the  Lumner  Brodhun  prism  set, 
where  they  are  redirected  to  the  eye-piece  in  the 
side  of  the  box.  The  other  end  of  the  prism 
compartment  contains  a  milk  glass  window  illum- 
inated from  behind  by  a  comparison  lamp  at  the 
further  end  of  the  box.  This  lamp  can  be  moved 
back  and  forth  to  secure  a  balance.  When  a 
balance  is  obtained,  the  intensity  is  read  directly 
on  a  scale  in  the  side  of  the  box,  the  scale  being 
based  on  the  law  of  inverse  squares. 

Candle-Power  Relations 

The  candle-power  as  a  unit  of  light  intensity 
was  originally  determined  by  the  horizontal  in- 
tensity of  light  from  a  certain  specified  candle 
known  as  the  British  standard  candle.  But 
since  the  value  can  be  more  accurately  pre- 
served and  reproduced  in  the  incandescent  lamp, 
this  arbitrary  value  is  now  maintained  in  tested 
incandescent  lamps  in  the  U.  S.  Bureau  of  Stand- 
ards at  Washington  and  in  other  laboratories. 
The  present  standard  in  general  use  in  the 
United  States,  Great  Britain,  France  and  other 


countries  (Germany  excepted),  is  the  Inter- 
national Candle-power,  which  was  established 
at  the  International  Conference  of  1909.  It  js 
1.6%  less  than  the  British  candle  used  in  this 
country.  Thus  16  British  candle-power  corres- 
ponds to  16.26  International  candle-power. 

The  relations  of  the  International  Candle  to 
other  terms  are  as  follows; 

1  International   Candle  =  1  American  Candle 
United  States) . 

1  International  Candle  =  1  Pentane   Candle 
(Great  Britain) . 

1  International  Candle  =  1  Bougie  Decimale 
or  0.104  Carcel  Units.     (France) . 

1  International  Candle  =  1.11   Hefner  Units 
(Germany). 

For  a  more  detailed  description  reference  is 
made  to  U.  S.  Bureau  of  Standards  Circular  No. 
15,  dated  May  20,  1909. 

In  the  case  of  the  incandescent  lamp  it  has 
become  customary  to  rate  a  lamp  in  terms  of  the 
mean  horizontal  candle-power  with  clear  bulb 
and  no  reflectors. 

The  horizontal  candle-power  measurement  was 
adopted  simply  because  it  was  the  customary 
and  most  convenient  method  of  measuring  the 
light  intensity  of  gas,  oil,  and  candle  flames, 
which  burn  generally  in  a  vertical  direction.  In- 
candescent lamps,  however,  may  be  used  in  any 
and  every  position,  and  in  addition  it  is  possible 
to  alter  considerably  the  distribution  of  light 
from  an  incandescent  lamp  by  the  simple  pro- 
cess of  changing  the  shape  of  the  filament.  As 
horizontal  measurement  of  candle-power  disre- 
gards all  light  emitted  save  that  emitted  in  a 
horizontal  direction,  and  as  light  sources  giving 
widely  different  total  amounts  of  light  may  emit 
the  same  amount  of  light  in  a  horizontal  direc- 
tion, it  obviously  follows  that  this  method  of 
candle-power  measurement  is  incomplete,  espec- 
ially when  lamps  of  different  types  of  filaments 
are  compared.  Furthermore,  with  any  type  of 
lamp  the  intensity  of  light  varies  in  different  di- 
rections, particularly  for  various  angles  of  eleva- 
tion. It  is  moreover  modified  by  the  use  of 
globes  and  reflectors.  Therefore  a  candle-power 
rating  of  a  lamp  has  no  value  (except  in  the  case 
of  a  standard  type  of  incandescent  lamp)  unless 
the  equipment  used  and  the  candlepower  re- 
ferred to  are  fully  described. 

A  full  and  complete  measure  of  candle  power 
requires  consideration  of  the  light  given  in  all 
directions,  or  at  all  points  of  a  sphere  surround- 
ing the  lamp.  If  we  take  the  mean  of  all  these 
candle-power  values  we  have  what  is  termed  the 
mean  spherical  candle-power.  The  mean  spher- 
ical candle-power  may  then  be  considered  as  a 
measure  of  the  total  flux  of  light. 
M.  S.  C.  P.  X  4  IF  =  total  lumens  emitted. 


The  complete  measurement  of  spherical  can- 
dle-power of  incandescent  lamps  involves  con- 
siderable work  with  special  apparatus.  It  is 
possible,  however,  to  express  approximately  the 
mean  spherical  candle-power  in  terms  of  the 
mean  horizontal  candle-power  and  a  spherical 
reduction  factor. 

The  spherical  Candle-power  Factor  or  Reduc- 
tion Factor  of  a  lamp  is  the  ratio  of  its  Mean 
Spherical  to  its  Mean  Horizontal  Candle-power,  or 
Mean  Spher.  C.  P.  -f  Mean  Horiz.  C-  P. 

Example:  -The  Spherical  Candle-power  Factor 
of  a  lamp  whose  Mean  Horizontal  Candle-power 
is  33.9,  and  whose  Mean  Spherical  Candle-power 
is  26.44,  is  equal  to  26.44  -r  33.9  =  .78. 

The  Spherical  Reduction  Factors  for  tungsten 
filament  and  metallized  filament  lamps  are  as 
follows: — 

Mazda 

Compensator  type 79 

Tubular 78 

Train  Lighting       80 

Round  Bulb,  15  W-250  W,  100-130  volt  .78 
All  other  large  styles      - 79 

Gem 
Regular 825 

Train  Lighting 8»5 

The  Mean  Horizontal  Candle-power  is  the 
mean  of  the  candle-power  in  all  directions  either 
above  or  below  the  horizontal.  When  above  it 
is  designated  as  mean  upper  hemispherical  can- 
dle-power. Mean  lower  hemispherical  candle- 
power,  i.e..  below  the  horizontal,  is  understood 
when  merely  mean  hemispherical  candle-power 
is  specified,  This  unit  is  then  a  measure  of  the 
flux  of  light  in  its  hemisphere.  Lumens  (in 
lower  hemisphere)  =  2^  M.  Hemispherical  C.P. 
The  lumen  is  the  unit  of  the  flux  either  of  light 
or  of  illumination,  and  is  equal  to  the  intensity 
distributed  over  one  unit  of  space.  Ex. -Lumens 
(of  light)=:  C.P.  X  radians  of  solid  angle.  There 


dies  X  square  feet  of  area. 

The  lumens  of  light  correspond  directly  to 
those  of  illumination,  so  that  if  all  the  lumens 
from  a  light  source  fall  upon  a  surface,  the  lum- 
ens of  light  and  of  illumination  will  be  equal. 

For  practical  service  and  in  the  commercial 
rating  of  lamps  the  mean  horizontal  candle- 
power  is  still  in  use,  but  in  testing  and  compar- 
ing lamps  of  different  shape  filaments  the  mean 
spherical  candle-power  should  be  considered  for 
the  following  reasons  which  apply  to  lamps  of 
any  one  class  of  filament. 

The  life  and  candle-power  performance  of  a 


lamp  depend  upon  the  temperature  of  its  fila- 
ment. It  is  not  practicable  to  measure  this  tem- 
perature in  degrees,  and  since  with  similar 
conditions  of  vacua  and  filament  surfaces  the 
temperature  is  indicated  by  the  consumption  of 
power  per  candle  or  watts  per  candle,  we  utilize 
watts  per  candle  as  a  basis  for  determining  rela- 
tive temperatures  or  the  relative  measure  of 
strain  upon  filaments  while  operating. 

As  watts  per  candle  is  a  ratio  of  watts  con- 
sumed to  total  candle-power  given,  it  is  appar- 
ent that  the  method  of  obtaining  the  candle- 
power  has  an  important  bearing  in  determining 
the  relative  strain.  When  the  horizontal  candle- 
power  is  taken,  the  watts  per  candle  determine 
the  relative  strain  correctly,  only  when  the  fila- 
ments are  exactly  alike  in  shape.  With  spherical 
candle-power,  however,  the  watts  per  candle 
determine  correctly  the  relative  strain  between 
filaments  no  matter  what  their  size  or  shape. 
If,  therefore,  a  test  be  made  between  lamps  hav- 
ing filaments  differing  in  shape,  we  must  com- 
pare them  at  the  same  watts  per  mean  spherical 
candle-power  and  not  at  the  same  watts  per 
mean  horizontal  candle-power.  This  can  be  ac- 
complished by  either  of  two  methods,  viz.:— 

1.  By  testing  the  lamps  at  the  same  watts 
per  mean  spherical  candle-power,  or 

2.  By  testing  the  lamps  at  the  same  watts 
per  mean  horizontal  candle-power,  and  calculat- 
ing their  lives  at  the  same  watts  per  mean  spher- 
ical candle-power  by  means  of  their  spherical  and 
horizontal  candle-powers   and  their  life  factors, 
Ex.:— 

Suppose  two  lamps,  A  and  B,  are  placed  on 
test  at  1.23  watts  per  Mean  Horizontal  Candle- 
power,  and  that 

=  x  282    and 


Mean  Spher.  C.  P. 
.Mean  Hor.  C.P. 
Mean  Spher.  C.  P. 
Then 

Watts  per  Mean  Spher.  C.P.  of  A  =  1.23  X  1.282 
=1.577. 

Watts  per  Mean  Spher.  C.P.  of  B  =  1.23  X  1.208 
=  1.486. 

Considering  the  watts  per  M.S. C.P.  of  A  as 
100%,  the  watts  per  M.S. C.P.  of  B  will  be  94.3%, 
and  the  life  factor  of  B  is  68%.  Therefore  to  re- 
duce lamp  B  to  an  equal  comparative  basis  with 
lamp  A  we  must  multiply  B's  result  by  .68. 

Efficiency  of  a  lamp  or  light  source  is  expressed 
in  terms  of  specific  consumption,  or  specific  out- 
put, as  watts  per  mean  spherical  candle-power, 
total  lumens  per  watt,  lumens  per  cubic  foot  of 
gas  or  per  gallon  of  oil.  In  the  case  of  the  in- 
candescent lamp  it  is  customary  to  use  watts  per 


candle-power  (Mean  Horizontal).  Lumens  per 
watt  is,  however,  a  more  reliable  measure  and 
will  probably  be  used  to  a  greater  extent,  if  not 
altogether  in  the  near  future. 

The  rated  or  commercial  efficiency  of  a  lamp 
is  its  initial  efficiency  or  efficiency  when  new. 
As  the  efficiency  of  a  lamp  changes  during  its 
life  it  is  obvious  that  its  average  efficiency  is 
quite  different  from  its  initial  efficiency  and 
should  be  carefully  distinguished  from  it. 

The  candle-power  and  voltage  of  a  lamp  are 
fixed  by  its  initial  efficiency  (W.P.C  ),  and  the 
three  terms,  candle-power,  voltage,  and  watts 
per  candle  are  necessary  for  a  complete  express- 
ion of  a  lamp's  rating. 


Illumination  Calculations 

Relations  of  Foot  Candles,  Candle-Power,  and 

Distance  between  the  Source  of  Light 

and  the  Surface  Illuminated. 

Consider  a  light  of  1  candle-power  intensity  in 
all  directions  placed  at  the  center  of  a  hollow 
spherical  shell  of  1  ft.  radius.  This  light  would 
illuminate  the  inner  surface  with  an  intensity  of 
1  ft.  candle,  and  the  illuminated  area  would  be 
4  if  —  (12.56)  sq.  ft.,  since  the  surface  of  a  sphere 
is  found  by  multiplying  the  square  of  the  radius 
by  the  constant  4  if.  If  the  same  light  were 
placed  at  the  center  of  a  spherical  shr-11  of  2  ft. 
radius,  the  quantity  of  light  originally  distributed 
over  the  area  of  4  if  sq.  ft.  would  now  be  distri- 
buted over  an  area  of  four  times  4  if,  (50.28)  sq.  ft. 
It  is  readily  seen  that  the  illumination  on  the 
larger  surface  would  be  1A  of  a  foot  candle,  since 
the  total  amount  of  light  is  the  same  in  both 
cases,  and  the  larger  surface  is  four  times  the 
smaller.  A  lamp  of  16  spherical  candle  power  at 
the  center  of  the  smaller  sphere  would  give  an 
illumination  of  16  foot  candles  on  the  innersurf  ace. 
If  placed  at  the  center  of  the  larger  sphere  the 
illumination  on  the  inner  surface  would  be  4  foot 
candles.  If  placed  at  the  center  of  a  hollow 
sphere  of  4  ft.  radius  the  illumination  on  the 
inner  surface  would  be  1  foot  candle. 

If  a  light  source  be  located  at  the  center  of  a 
spherical  surface  all  the  light  rays  emanating 
therefrom  will  meet  this  surface  normally :  hence, 
normal  illumination  in  foot  candles  is  found  by 
dividing  the  candle-power  of  the  source  by  the 
square  of  its  distance  from  the  surface  illuminated . 

Therefore,  normal  illumination  = 

Candle-power  (c.p.) 
Distance  squared  (da) 

12 


This  rule,  known  as  "The  Law  of  Inverse 
Squares"  does  not  apply  where  the  light  falls  ob- 
liquely on  the  surface  under  consideration,  nor 
where  the  source  is  a  long  line,  as  the  Moore  tube. 

Calculation   of    Horizontal    Illumination    (Point 
by  Point  Method) 

THIS  is  THE  FUNDAMENTAL  OR  BASIC  METHOD 


Fig.  6 

In  practical  illumination  most  of  the  rays  do 
not  meet  the  surface  normally.  In  Fig.  6  the 
rays  from  the  lamp  shown  at  "S"  are  assumed  to 
be  normal  to  the  plane  "AB".  As  has  been 
shown  the  illumination  on  this  plane  is 
_c.p. 


In=' 


d2 


(1). 


C.P.  equals  candle-power  of  the  lamp  at"S";  d 
equals  distance  "SA". 

But  in  reality  the  light  that  would  have  been 
intercepted  by  "AB"  will  be  distributed  over  the 
larger  plane  "AC".  From  the  triangle  ABC 

rr-     =  cos  a  .........  (2)      hence, 


AC  = 


........  (3). 


that  is,  the  square  feet  in  plane  AC  is  found  by 
dividing  the  square  feet  in  AB  by  the  cos  a.  To 
illustrate,  if  a  had  such  a  value  as  to  make  its  cos 
equal  to  .5,  the  area  of  the  plane  AC  would  be 
found  by  dividing  that  of  AB  by  .5,  that  is,  area 
AC  would  be  twice  as  great  as  AB,  and  the  in- 
tensity of  illuminati- >n  would,  therefore,  be 
one-half  that  of  AB 

Hence  the  general  rule  that  since  the  area  of 
the  oblique  plane  AC  is  obtained  by  dividing  that 
of  the  normal  plane  AB  by  cos  a,  the  illumination 
of  AC  is  thai  of  AB  multiplied  by  cos  a,  or  for 
oblique  illumination, 

Ih  — ~bjr     cos  a (4) 

But  from  the  triangle  OSA 
13 


1.    Table   of   Angles,    Sines   and 
Cosines. 


a° 

sin  a 

sinaa 

cos  a 

cos2a 

cos3a 

0     .0 

.0000 

1.000 

1.000 

1.000 

1    .0175 

.0000 

1.000 

1.000 

1.000 

2   |  .0349 

.0000 

.999 

.999 

.998 

3 

.0523 

.0001 

.999 

.997 

.996 

4 

.0698 

.0003 

.998 

.995 

.993 

5 

.0872 

.0007 

.996 

.992 

.989 

6 

.105 

.0011 

.995 

.989 

.984 

7 

.122 

.0018 

.993 

.985 

.978 

8 

.139 

.0027 

.990 

.981 

.971 

9 

.156 

.0038 

.988 

.976 

.964 

10 

.174 

.0052 

.985 

.970 

.955 

11 

.191 

.0069 

.982 

.964 

.946 

12 

.208 

.0090 

.978 

.957 

.936 

13 

.225 

.0114 

.974 

.949 

.925 

14 

.242 

.0142 

.970 

.941 

.913 

15 

.259 

.0173 

.966 

.933 

.901 

16 

.276 

.0209 

.961 

.924 

.888 

17 

.292 

.0250 

.956 

.915 

.875 

18 

.309 

.0295 

.951 

.905 

.860 

19 

.326 

.0345 

.946 

.894 

.845 

20 

.342 

.0400 

.940 

.883 

.830 

21 

.358 

.0460 

.934 

.872 

.814 

22 

.375 

.0526 

.927 

.860 

.797 

23 

.391 

.0596 

.921 

.847 

.780 

24 

.407 

.0673 

.914 

.835 

.762 

25 

.423 

.0755 

.906 

.821 

.744 

26 

.438 

.0843 

.899 

.808 

.726 

27 

.454 

.0936 

.891 

.794 

.707 

28 

.470 

.104 

.883 

.780 

.688 

29 

.485 

.114 

.875 

.765 

.669 

30 

.500 

.125 

.866 

.750 

.650 

31   i  .515 

.137 

.857 

.735 

.630 

32     .530 

.149 

.848 

.719 

.610 

33 

.545 

.162 

.839 

.703 

.590 

34 

.559 

.175 

.829 

.687 

.570 

35 

.574 

.189 

.819 

.671 

.550 

36 

.588 

.203 

.809 

.655 

.530 

37 

.602 

.218 

.799 

.638 

.509 

38 

.616 

.233 

.788 

.621 

.489 

39 

.629 

.249 

.777 

.604 

.469 

40 

.643 

.266 

.766 

.587 

.450 

41 

.656 

.282 

.755 

.570 

.430 

42 

.669 

.300 

.743 

.552 

.410 

43 

.682 

.317 

.731 

.535 

.391 

44 

.695 

.335 

.719 

.517 

.372 

45 

.707 

.354 

.707 

.500 

.354 

Table    of    Angles,    Sines    and 
Cosines — Continued. 


a<> 

sin  a 

'  sin:5a 

cos  a 

cos  -a 

cossa 

46 

.719 

.372 

.695 

.483 

.335 

47 

.731 

.391 

.682 

.465 

.317 

48 

.743 

.410 

.669 

.448 

.300 

49 

.755 

.430 

.656 

.430 

.282 

50 

.766 

.450 

.643 

.413 

.266 

51 

.777 

.469 

.629 

.396 

.249 

52 

.788 

.489 

.616 

.379 

.233 

5A 

.799 

.509 

.602 

.362 

.218 

54 

.809 

.530 

.588 

.345 

.203 

55 

.819 

.550 

.574 

.329 

.189 

56 

.829 

.570 

.559 

.313 

.175 

57 

.839 

.590 

.545 

.297 

.162 

58 

.848 

.610 

.530 

.281 

.149 

59 

.857 

.630 

.515 

.265 

.137 

60 

.866 

.650 

.500 

.250 

.125 

61 

.875 

.669 

.485 

.235 

.114 

62 

.883 

.688 

.470 

.220 

.103 

63 

.891 

.707 

.454 

.206 

.0936 

64 

.899 

.726 

.438 

.192 

.0842 

65 

.906 

.744 

.423 

.179 

.0755 

66 

.914 

.762 

.407 

.165 

.0673 

67 

.921 

.780 

.391 

.153 

.0597 

68 

.927 

.797 

.375 

.140 

.0526 

69 

.934 

.814 

.358 

.128 

.0460 

70 

.940 

.830 

.342 

.117 

.0400 

71 

.946 

.845 

.326 

.106 

.0345 

72 

.951 

.860 

.309 

.0955 

.0295 

73 

.956 

.8)5 

.292 

.0855 

.0250 

74 

.961 

.888 

.276 

.0,60 

.0209 

75 

.966 

.901 

.259 

.0670 

.0173 

76 

.970 

.914 

.242 

.0585 

.0142 

77 

.974 

.925 

.225 

.0506 

.0114 

78 

.978 

.936 

.208 

.0432 

.0090 

79 

.982 

.946 

.191 

.0364 

.0070 

80 

.985 

.955 

.174 

.0302 

.0052 

81 

."88 

.964 

.156 

.0245 

.0038 

82 

.990 

.971 

.139 

.0194 

.0027 

83     .993 

.978 

.122 

.0149 

.0018 

84     .995 

.984 

.105 

.01(9 

.0011 

85     .996 

.989 

.0872 

.0076 

.0007 

86 

.9976 

.993 

.0697 

.0048 

.0003 

87 

.9986 

.996 

.0523 

.0027 

.0001 

88 

.9993 

.998 

.0349 

.0012 

.0000 

89 

.9998 

1.000 

.0175 

.0003 

.0000 

90 

1.000 

1.000 

.0000 

.0000 

.0000 

s 

I 


o 

8888888S.S;8:8:8:888;8:8;S.888.88:ll8 


ir 


«?'3 

•i? 


ilisilliilill 


oopooooc 


i§s§23|||s 

sppppppopc 


8ooo88o 


ppppppSqpppppSpopSS 


•pajisap  si  uoiieuuunin 

jo  Xiisuaiui  aaaqM.  miod   01  aoanos   iqSjl  Japuri 
'  ,oajtp  luiod    uiojj  jaaj  in  aouBjsip   JB;UOZUOH 


82 
8E 


il 


16 


h        SO  ,_. 

—  =  — — -  =  cos  a (5)     or, 

d       SA 

d=-h—=  (6) 

cos  a 

Squaring,  d2  =  -~- (7) 

cos2  a 

Substituting  for  d2  in  equation  (4) 

lh  =        -      cos»a (8) 


values  of  a  from  1  to  90°. 

To  facilitate  the  use  of  the  above  formula  there 
are  given  in  Table  2,  values  of  illumination  on 
horizontal  planes  at  different  heights  and  at 
different  horizontal  distances  of  a  light  source  of 
1  candle-power  and  also  the  corresponding  angles 
made  by  the  light  rays  with  the  perpendicular 
to  the  plane. 

Method  of  Using:  Table 

From  the  lamp  and  reflector  in  use  obtain  the 
distribution  curve.  Take  from  Table  2  the 
value  (in  foot  candles)  of  illumination  which  a  one 
candle-power  light  source  would  produce  at  the 
point  selected.  Also  note  the  angle  corres- 
ponding to  this  point.  From  the  distribution 
curve  of  the  lamp  take  the  candle-power  at  the 
corresponding  angle.  Multiply  this  value  by  the 
illumination  value  found  in  the  table,  and  the 
resulting  value  will  be  the  illumination,  in  foot 
candles  at  the  point  selected,  of  the  lamp  under 
consideration. 

For  example  :  required  the  illumination  pro- 
duced by  a  60  watt  clear  Mazda  lamp  with  intensive 
type  Holophane  reflector  at  a  point  12  ft.  below 
and  12  ft.  to  one  side  of  the  lamp.  From  Table  2 
the  vahte  corresponding  to  these  distances  is 
.0025  foot  candles  and  the  corresponding  angle  is 
45C.  From  the  distribution  curve  of  the  60  watt 
lamp  with  intensive  type  reflector  on  Page  31  the 
candle-power  at  45°  is  approximately  64.  Then 
.0025  x  64  =  .16  which  is  the  illumination  at  the 
point  selected. 

If  there  be  more  than  one  lamp  in  the  room ,  the 
illumination  produced  by  each  lamp  is  found  in 
thfe  above  manner,  and  the  sum  taken  for 
the  total  illumination  at  the  point  under 
consideration. 

Calculation  of  Vertical  Illumination 

Suppose  it  is  desired  to  calculate  the  illumina- 
tion I  on  a  vertical  plane  through  A.  The  light 
rays  that  would  have  fallen  on  AB  will  be  inter- 
cepted by  the  vertical  plane  DA. 

From  triangle  ABD 

17 


AB 

AD 
Then 


.........  (10) 


sin  a 

that  is,  the  square  feet  in  AD  is  found  by  divid- 
ing the  square  feet  in  AB  by  the  sin  a.  To 
illustrate,  —  if  a  had  such  a  value  as  to  make  sin  a 
equal  to  .866  the  area  of  the  plane  AD  would  be 
found  by  dividing  the  area  of  AB  by  .866.  In 
other  words,  the  area  of  AD  would  be  1/.866  times 
that  of  AB  and  the  intensity  of  illumination  on 
AD  would  eaual  .866  of  that  on  AB. 

In  general  then,  the  intensity  of  illumination 
on  a  vertical  plane  is  equal  to  that  on  the  normal 
plane,  multiplied  by  the  sin  a 


.........  (11) 


From  triangle  OSA 


OA      / 

-5-7-  —  -r  —  sin  a    .........  (12) 

oA         Q 

ord=     /         .........  (13) 

sin  a 

/2 

squaring,  d2  =  -T- 


sin2  a 
then  in  equation  (11) 

/2 

Iv  =  c.  p.  sin2a  -~  -7-=-         ........  (15) 

sin2  a 

=  ^sin«a    .........  (16) 

The  values  of  sin3  a  are  given  in  Table  1. 

Flux  of  Light  Method  of  Calculating  Horizontal 
Illumination. 

For  rapid  calculation  the  following  tables  and 
formulae  will  be  found  convenient  : 

As  stated  under  "Candle-power  Relations,"  a 
lumen  is  the  quantity  of  light  required  to  illu- 
minate 1  sq.  ft.  area  with  an  intensity  of  1  ft. 
candle.  Now  from  Table  8  can  be  determined 
the  intensity  of  illumination  in  foot  candles 
recommended  as  satisfactory  for  various  classes 
of  service.  The  floor  area  of  the  '"oom  is  known 
and  the  product  of  foot  candles  times  sq.  ft.  floor 
area  equals  effective  lumens  required.  Having 
ascertained  the  effective  lumens  required,  there 
are  two  methods  by  which  the  number  and  sizes 
of  lamps  necessary  can  be  determined. 

The  efficiency  of  an  illumination  effect  can  be 
expressed  in  effective  lumens  per  watt,  which  is 
equal  to  the  foot  candles  divided  by  watts  per 
sq.  ft.  This  shows  the  distinction  between 
total  lumens  as  emitted  by  a  light  source 


and  effective  lumens  as  received  on  some  surface 
or  working  plane. 

As  a  result  of  numerous  experiments  the  effec- 
tive lumens  per  watt  for  various  lamps  and 
reflector  equipments  and  conditions  of  walls  and 
ceilings,  has  been  determined.  These  values 
are  shown  below  in  Table  3. 

3.     Effective  Lumens  per  Watt 

Lamp  Equipment  Ceiling    Walls  Constant 

Mazda  Clear  Holophane  Refl.  Light  Light  5.0 
Mazda  Clear  Holophane  Refl.  Light  Dark  4.0 
Mazda  Clear  Holophane  Refl.  Dark  Dark  3.4 
Gem  Clear  Holophane  Refl.  Light  Light  2.2 
Gem  Clear  Holophane  Refl.  Light  Dark  1.8 
Gem  Clear  Holophane  Refl.  Dark  Dark  1.5 

By  dividing  the  total  effective  lumens  required 
by  the  proper  constant  from  the  above  table,  the 
total  wattage  required  is  obtained.  This  wattage 
is  divided  by  the  necessary  number  of  lamps 
(method  of  determining  this  is  shown  later)  to 
get  the  watts  per  lamp. 

The  other  of  the  two  schemes  mentioned 
above  is  as  follows:  Illumination  tests  have 
shown  that  with  certain  lamps,  reflectors,  and 
wall  conditions,  a  given  percentage  of  the  total 
lumens  emitted  by  the  lamp  reaches  the  working 
plane  and  the  percentage  is  called  the  illumina- 
tion constant  for  that  particular  equipment 
(Table  4). 

Hence,  if  the  total  effective  lumens  required  be 
divided  by  this  illumination  constant,  the  total 
lumens  emitted  by  the  lamp  is  determined.  Di- 
viding this  by  the  required  number  of  lamps  will 
give  the  total  lumens  per  lamp.  The  total  lumens 
given  by  any  of  the  standard  lamps  is  shown 
in  Table  5. 


4.     Illumination  Constants 


Lamp 

Equipment 

Ceiling 

Walls 

Constant 

Mazda 
Mazda 
Mazda 
Gem 
Gem 
Gem 

* 

Clear 
Holophane 
Rfl. 

Light 
Light 
Dark 
Light 
Light 
Dark 

Light 
Dark 
Dark 
Light 
Dark 
Dark 

.64 
.51 
.43 
.57 

.45 
.38 

5.    Total  Lumens  Given  by  Different 
Types  of  Incandescent  Lamps 


RATED 

MAZDA  OR 
TUNGSTEN 

GEM 

CARBON 

WATTS 

100  v 

200,,. 

100  v 

100  v 

200  v 

130  V" 

260  V' 

130  V' 

130  v' 

250  V 

10 

21. 

15 

112. 

20 

151. 

50. 

25 

185. 

84. 

30 

96. 

35 

84. 

40 

320. 

160. 

45 

300. 

50 

205. 

175. 

60 

500. 

400. 

250. 

210. 

170. 

80 

335- 

100 

830. 

670. 

420. 

350. 

120 

420. 

340. 

150 

1250. 

1000. 

250 

2170. 

400* 

3470. 

1670. 

500* 

4330. 

4030. 

*Round  bulb  lamps.  All  other  lamps  given 
here  have  regular  type  straight  sided  bulbs. 

Determining:  the  Number  of  Lamps 

The  area  to  be  lighted  should  be  divided  as 
nearly  as  possible  into  equal  squares  and  the 
light  unit  placed  at  the  center  of  each  square. 
The  size  of  the  square  depends  in  some  cases 
upon  the  extent  to  which  shadows  will  be  objec- 
tionable and  in  general  the  smaller  the  square 
the  less  intense  will  be  the  shadows.  In  lighting 
large  offices  where  individual  desk  lights  are  not 
employed,  the  square  should  be  comparatively 
small  in  order  to  have  the  light  on  any  one  desk 
coming  from  many  units.  Table  6  gives  the  de- 
sirable sizes  of  squares  for  various  classes  of 
service. 

Having  determined  the  wattage  of  the  lamps, 
the  number  to  be  used  and  the  spacing,  there 
remains  the  choice  of  the  reflector. 


Choice  of  Reflector 

In  selecting  a  reflector,  a  careful  study  of  the 
dimensions  of  the  room  is  necessary,  in  general, 
an  extensive  type  of  reflector  should  be  used  for 
stores  where  there  is  a  single  row  of  lights  illu- 
minating both  show  cases  and  shelves,  also  for 
large  areas  with  low  ceiling. 

20 


w  w 

H  ft 

|p 

=  ^J 

p  p  q  q  q  p  q  c>  5  £  5 
Q 

fi  I 

I 
| 

1        ,:,,,:,,.,:^         g 

p        Q  o  t-i  t-i  Q  p  i*  p  p  p  $H         gj 
3 


t/2  w  tn 
-*-<  -*->  -*-> 

42.5?.5P.Sf 


§ 
5 


2 

« 


0,       ... 

2 


I*" 

o 

K 


If  the  area  to  be  lighted  is  small  or  requires 
high  intensity  of  illumination,  an  intensive  re- 
flector is  used.  Examples  may  be  found  in 
restaurants,  department  stores,  etc. 

Focusing-  reflectors  are  used  in  show  windows, 
offices,  and  other  places  where  high  intensities 
are  required. 

Table  7  shows  the  proper  height  for  lamps  in 
terms  of  distance  between  units. 
Application  of  the  Foregoing:  Paragraphs 

As  an  example  of  the  above  rules,  the  "flux  of 
light  "  method  is  used  for  the  following  specific 
case : 

A  shoe  store  50  ft.  x  150  ft.  with  a  12  ft.  ceiling, 
light  ceiling  and  side  walls,  lined  with  shelves 
containing  boxes  is  to  be  illuminated. 

From  the  table  of  foot  candle  intensities 
recommended  for  classes  of  service, 

Shoe  stores,  2.0  —  4.0,  taking  3  as  an  average. 

Floor  area,  50  x  150  =r  7500  sq  ft. 

Effective  lumens  required,  7500  x  3  =  22,500. 

Since  prismatic  glass  reflectors  are  very  effi- 
cient, are  sufficiently  decorative  for  this  class  of 
service,  and  the  Holophane  are  the  best  made 
and  most  efficient  of  this  class  of  reflectors,  it  is 
applicable  here. 
First  Method 

In  Table  3  for  clear  Holophane,  light  walls  and 
ceiling,   the  effective  lumens    per   watt   are   5. 
Hence,  22,500  ~  5  gives  4500  watts  required. 
Second  Method 

The  illumination  constant  (Table  4)  for  clear 
Holophane,  light  ceiling  and  light  walls,  is  .64. 
Hence,  22,500  -j-  .64  gives  35,150  total  lumens 
required. 

Next,  referring  to  the  table  of  desirable  sizes 
of  squares  is  found,—  "stores,  11  to  15  ft.  ceiling 
height,  10  to  16  ft.  squares."  For  a  symmetrical 
arrangement  the  size  of  the  squares  will  be  taken 
as  \2%  ft.,  making  four  rows  of  twelve  lamps 
each,  a  total  of  48  lamps.  Then,  4500  watts  -r  48 
gives  93.8  watts  per  lamp.  Taking  the  100  watt 
lamp  as  the  nearest  size.  Or  35,150  total  lumens 
~  48  =  732  lumens  per  lamp.  From  Table  5  the 
60  watt  Mazda  lamp  gives  500  total  lumens  and 
the  100  watt  830  total  lumens.  The  100  watt  lamp 
should  be  used  as  it  is  better  to  run  a  little  above 
the  calculated  value  than  to  drop  a  marked 
amount  below  it. 

If  it  is  desired  to  more  closely  approach  the 
values  calculated,  the  rows  of  lamps  may  be 
spaced  12%  ft.  apart,  and  in  the  rows  the  lamps 
may  be  spaced  13}£  ft.  apart,  making  a  total  of 
44  —  100  watt  lamps. 

In  a  shoe  store  the  plane  of  illumination  is 
about  1  ft.  from  the  floor,  where  inspection  of  the 
shoes  is  made,  and  there  must  be  sufficient  dif- 
fused light  on  the  boxes  to  enable  the  clerk  to 
read  the  labels.  With  the  above  arrangement 

22 


of  lamps  and  conditions  to  be  met,  the  inten- 
sive type  of  Hplophane  reflector  is  applicable. 
The  average  distance  between  lamps  is  13  ft. 
As  shown  in  Table  7  the  hanging  height  for 
intensive  reflectors  should  be  %  of  the  distance 
between  lamps. 

%  X  13  =  10.4  or,  say,  10K  ft.  from  the  working 
plane  or  the  surface  to  be  illuminated.  The 
lamps  should  then  be  hung  about  11>£  ft.  from 
the  floor. 

As  a  summary  of  the  foregoing  calculations, — 
44  — 100  wait  bowl  frosted  Mazdalamps,  equipped 
with  intensive,  clear,  Holophane  reflectors,  form 
H  holders,  spaced  12%  x  13>£  ft.,  hung  with  the 
center  of  the  lamp  about  11  %  ft.  from  the  floor. 


8.     Foot -Candle    Intensities    Recom- 
mended for  Various  Classes  of  Service. 

Armory  or  Drill  Hall 2.0 

Armory   (Cavalry — tan-bark  floor) 3.0 

Art  Gallery   (walls) 5.0  —10.0 

Auditorium 1.0  —  3.0 

Automobile  Showroom 3.0  —  6.0 

Automobile  (interior) 5  —  1.0 

Ball  Room 2.0  —  3.0 

Bank  (general) 2.0  —  3.0 

Bank  (desk  work) 4.0  —  6.0 

Bar  Room 2.0  —  5.0 

BarberShop  (over  chairs) 3.0  —  6.0 

Bath  (public) 

Dressing  rooms .7  —  1.0 

Swimming  pool 1.5  —  2.0 

Billboard 5.0  —15.0 

Billiard  Room  (general) .8  —  1.5 

Billiard  Room    (with  distributed  and 
diffused  light) 6.0  —10.0 

Book  Binding. 

Folding,  Assembling,  Pasting,  etc.  2.0  —  3.0 
Cutting,  Punching  and  Stitching. .  3:0  —  5.0 
Embossing 4.0  —  6.0 

Bowling  Alley. 

Alley 1.5 

Pins 4.0 

Cafe  (general  illumination  only) 2.0  —  4.0 

Cafe  (lights  on  tables) 1.0  —  2.0 

Canning  Plants. 

Pressing  Tables 1.0  —  1.5 

Filling  Tables 1.0  —  1.5 

Packing  Tables  (dried  fruits) 1.5  —  2.5 

Preserving  Caldrons 2.0  —  2.5 

Coffee  Roasting  at  Tables 2.0  —  3.0 

Assorting  Tables 2.5  —  3.0 

Packing  Tables 1.0  —  2.0 

23 


Shipping  Rooms 2.0  —  3.0 

Card  Room 2.0  —  3.0 

Carpenter  Shop 2.0  —  5.0 

Cars. 

Baggage .7  —  1.0 

Day  Coach 2.0  —  3.0 

Dining  (general  illumination  only)  2.0  —  4.0 

Dining  (lights  on  tables) 1.0  —  20 

Mail 5.0  —10.0 

Pullman 2,0  —  4.0 

Street 2.0  —  3-0 

Church 1.0  —  2.5 

Club. 

For  various  rooms,  see  Bath,  Hotel, 
Residence,  etc. 

Cotton  Mill. 

Receiving  and  Opening  Bales .8  —  1.5 

Opening  and  Lapping 1.0  —  2.0 

Carding 1.5  —  2.5 

Drawing  Frame 1.5  —  2.5 

Roving,  Spooling,  Ring  Spinning, 

etc 2.0  —  3.0 

Warping 1.5  —  2.5 

Slashing 1.0  —  2.0 

Drawing  in 2.0  —  4.0 

Weaving  (light  goods) 2.0  —  4.0 

Weaving  (dark  goods 3.0  —  5.0 

Dyeing 2.0  —  3.0 

Dyeing  (inspection") 1.5  —  2.0 

Inspecting  (general)         5.0  —10.0 

Courts. 

Handball 7.0  —10.0 

Squash 7.0  —10.0 

Tennis 7.0  —10.0 

Court  Room .. 2.0        4.0 

Dairies  and  Milk  Depots 1.0  —  3.0 

Dance  Hall 2.0  —  4.0 

Depot  (see  Station  Railway). 

Desk <0  —  6.0 

Draughting  Room 6.0  —12.0 

Engraving 10.0  —12.0 

Factory. 

General    illumination  only,  where 
additional  special  illumination  for 
each  machine  or  bench  is  provided    .8  —  1.5 
Local    Bench    Illumination      (fine 

work) 5.0  —10.0 

Local  Bench  Illumination  (coarse 

work) 3.0  —  5.0 

Fire  Stations. 

When  the  alarm  is  turned  in 3.0 

At  other  times 1.0 

Forge  and  Blacksmithing 1.0  —  2.0 

Foundry 3.0 

24 


Garage 1.0  —  3.0 

Gymnasium 1.0  —  3.0 

Hall. 

See  Auditorium,  Corridor  of  Hole 
or  Office  Building. 

Hospital. 

Corridors .5 

Wards  (with  no  local  illumination 
supplied) 1.0  —  3.0 

Wards  ("with  local  illumination  sup- 
plied)   5 

Operating  Table 12.0  —20.0 

Hotel. 

Lobby 2.0  —  4.0 

Dining  Room  (general  illumina- 
tion only)  2.0  —  4.0 

Dining  Room  (lights  on  tables) 1.0  —  2.0 

Writing  Room 2.0  —  3.0 

Corridor .6 

Bed  Rooms 1.5  —  2.0 

Lavatory 1.5  —  2.0 

Laundry 2.0  —  3.0 

Library. 

Stack  Room 1.5  —  2.0 

Reading  Room  (with  no  local  il- 
lumination supplied) 3.0  —  4.0 

Reading  Room  (with  local  illumi- 
nation supplied) .7  —  1-5 

Lodge  Room 2.0  —  3.0 

Lunch  Room 2.0  —  4-0 

Machine  Shop. 

Machine  Tools  (fine  work) 5.0  —  8.0 

Machine  Tools  (coarse  work) 2.0  —  5.0 

Buffing  and  Grinding 2.0  —  3-0 

Bench  Work.     (See  Bench  Work). 

Assembling  and  Erecting 1.0  —  3.0 

Inspecting 4.0  —  7.0 

Market 3.0  —  5.0 

Moving-picture  Theater 1.0  —  1-5 

Museum 2.0  —  4.0 

Office  Lighting. 

Small  Offices  (officials) 3.0  —  4.0 

Small  Offices  (desks  against  walls)  3.0  —  6.0 
General  Offices  (accounting,  etc.)..  4.0  —  8.0 

Opera  House.     (See  Theater) . 

PaintShop  (fine  work) 4.0  —  8.0 

PaintShop  (coarse  work) 2.0  —  4.0 

Pattern  Shop  (wood) 3.0  —  5.0 

Pattern  Shop  (metal) 4.0  —  6.0 

Pool  Room.     (See  Billiard  Room) . 

Power  House 2.0  —  3.0 

Postal  Service 5.0  —10.0 

Printing. 

Linotype  and  Monotype 5.0  — 10.0 

Typesetting 6.0  —  8.0 

25 


Composing  Stone 6.0  —  8,0 

Matrixing  and  Casting 2.0  —  4. 

Proof  Reading 3.0  —  5. 

Presses 3.0  —5. 

Paper  Cutting,  Folding,  etc 2.0  —  4. 

Public  Square .1  —    .8 

Railway  Station. 

Waiting  Room 1.5  —  2.5 

Ticket  Offices,  etc.     (See  Offices). 

Rest  Room,  Smoking  Room,  etc....  1,0  —  2.0 

Baggage  Room .8  —  1.5 

Concourse 5  —     8 

Train  Platforms .5  —    .8 

Reading   (ordinary  print) 2.0  —4.0 

Reading  (fine  print) 3.0  —  5.0 

Residence. 

Porch .2  —  1.0 

Porch  (reading  light) 2-0  —  3.0 

Hall  (entrance) .7  —  1.0 

Reception  Room 1.0  —  3.0 

Parlor 1.0  —  3.0 

Sitting  Room 1.5  —  2.5 

Library 2.0  —  4.0 

Music  Room 2.0  —  3.0 

Dining  Room 1.5  —  2.5 

Dining  Room  Table   (with  dome)..  3.0  —  5.0 

Pantry 1.0  —  2.0 

Kitchen 2.0  —  3.0 

Laundry 1.5  —  2.0 

Hall  (upstairs) .5—    .8 

Bed  Room 1.0  —  3.0 

Bath  Room 2.0  —  3.0 

Furnace  Room .4  —    .8 

Store  Room .4  —    .8 

Restaurant.  (See  Hotel  Dining  Room) 

Rink  (skating) 1.0  —  3.0 

Rug  Rack 10.0  —20.0 

Saloon.     (See  Bar  Room). 
School. 

Class  Room 3.0  —  5.0 

Study  Room 3.0  —  5.0 

Assembly  Room 2.0  —  3.0 

Office 3.0  —  4.0 

Cloak  Room .7  —  1.0 

Corridor .8  —  1.0 

Manual  Training.     (See  Carpenter 
and  Machine  Shops). 

Laboratory 3.0  —  5.0 

Drawing.   <  See  Draughting  Room) 

Sewing,  Hand  (light  goods) 3.0  —  5.0 

Sewing,  Machine  (light  goods) 4.0  —  6.0 

Sewing,  Hand  (dark  goods) 4.0  —  8.0 

Sewing,  Machine   (dark  goods) 10  0  —15.0 

Shipping  Room 2.0  —  3.0 

Show  Window. 

Dry  Goods  Oiigh  grade) 15.0  —30.0 

Dry  Goods  (ordinary) 10.0  —20.0 

Dry  Goods  (smalltown) 5.0  —15.0 

26 


Miscellany  (large  city) 10.0  —20.0 

Miscellany  (smalltown) 5.0  —10.0 

Silk  Mills. 

Receiving 1.0  —  2.0 

Winding  Frames 2.0  —  4.0 

Throwing  Frames 2.0  —  4.0 

Quilling  and  Warping 3.0  —  5.0 

Weaving 4.0  —  6.0 

Dyeing 2-0  —  3.0 

Dyeing  Inspection .15.0  —25.0 

Finishing 3.0  —  5.0 

Sign.     (See  Billboard) . 

Stable .4  —  1.0 

Stamping  and  Punching  (sheet  metal)  2.0  —  5-0 

Station,  Railroad.     (See  Railway  Sta- 
tion) . 

Steel  Works. 

Executive    and    Clerical    Offices. 
(See  Offices). 

Drafting  Offices 4.0  —  8.0 

Machine    Shops.        (See   Machine 
Shops). 

Unloading  Yards .1  —    .3 

Open  Hearth  Floors,  Soaking  Pits 

and  Cast  Houses 1  —    .3 

Mould  Yard,  Skull  Cracker  Yard 

and  Ore  Yard 1  —    .3 

Loading  Yards  (inspection) 3—    .5 

Blast  Furnace  Cast  House .3  —    .5 

Rolling  Mills 1.0  —  2.0 

Wire  Drawing 1.0—  2.0 

Threading  Floors  of  Pipe  Mills 1.0  —  2.0 

Transfer  and  Storage  Bays .5  —  1.0 

Stock  Room 5  —  1.5 

Store. 

Art,   (Light  on  Exhibits) 5.0  —10.0 

Book 3.0  —  5.0 

Baker 2.0  —  4.0 

Butcher 2.0  —  4.0 

China 2.0  —  3.0 

Cigar 4.0  —  6.0 

Clothing 40  —  7.0 

Cloak  and  Suit 4-0  —  7.0 

Confectionery 3.0  —  5.0 

Decorator 4.0  —  5.0 

Department  (see  each  department) 

Drug 2.0  —  4.0 

Dry  Goods 4.0  —  7.0 

Florist 2-0  —  3.0 

Furniture 2.0  —  4.0 

Furrier 5.0  —  8.0 

Grocery 2.0  —  4.0 

Haberdasher.  (Men's  Furnishings)  5.0  —  7.0 

Hardware 2.0  —  4.0 

Hat 4.0  —  6-0 

Jewelry 4.0  —  6.0 

Millinery 4.0  —  6.0 

Music 2.0  —  4.0 

27 


Notions 3.0  —  5.0 

Piano 2.0  —  4.0 

Shoe 2.0  —  4.0 

Stationery 2.0  -   4.0 

Tailor 4.0  —  6.0 

Tobacco.     (See  Cigars). 
Street. 

Business,  (not  including  light  from 

show  windows  and  signs) .1  —    .2 

Residence 0  —  1.1 

Telephone  Exchange  (operators) 2.0  —  3.0 

Theater. 

Lobby 2.0  —  5.0 

Auditorium 1.0  —  2.5 

Warehouse .5  —  i  o 

Wharf .1  —    > 

Woolen  Mill. 

Picking  Table 2.0  —  4.0 

Washing  and  Combing 3.0  —  4.0 

Carding 1.5  —  2.5 

Twisting 2.0  —  3.0 

Dyeing 2.0  —  3.0 

Dyeing  (inspection) 15.0  —25.0 

Drawing  in 2.5  —  4.5 

Warping 3.0  —  5.0 

Weaving 4.0  —  6.0 

Weaving  (dark  goods) 6.0  —  8.0 

Perching 8.0  —15.0 


Reflectors  for  Use  with  Mazda  Lamps. 

Good  illumination  not  only  requires  sufficient 
light  but  the  proper  location  and  equipment  of 
the  lamps,  in  order  that  such  proper  distribution 
and  diffusion  of  light  may  result,  that  the  eye  is 
able  to  see  clearly  and  to  the  best  advantage 
without  strain  or  glare. 

Mazda  lamps,  due  to  their  construction,  give 
the  greatest  amount  of  light  in  a  horizontal  di- 
rection. Since,  in  general,  the  lamp  should  be 
located  above  the  line  of  vision  it  is  necessary  to 
use  reflectors  to  distribute  the  light  properly  and 
direct  it  upon  the  working  plane. 

Reflectors  may  be  divided  into  two  general 
classes,  namely,  industrial  and  decorative. 
These  however  overlap,  as  for  instance,  the 
prismatic  glass  reflector,  while  under  the  deco- 
rative class,  may  be  well  used  in  an  industrial 
layout. 

The  industrial  reflectors  are  primarily  of  metal 
with  reflecting  surface  of  porcelain  enamel  or 
aluminum  mat,  and  the  decorative  reflectors  of 
glass,  either  prismatic  or  opalescent. 

As  excellent  examples  of  these  types,  des- 
cription is  given  herewith  in  brief  of  several. 

28 


Industrial.  Mazda  Mill  Diffuser,  made  by  the 
General  Electric  Co.,  Schenectady,  N.  Y. 

This  is  a  sheet  metal  reflector,  heavily  porce- 
lain enameled.  The  metal  is  of  considerable 
thickness,  and  the  strength  of  the  reflector  re- 
markable, considerable  force  being  required  to 
even  bend  it  slightly.  The  porcelain  enamel  is 
smooth  and  of  several  coats,  making  an  excellent 
reflecting  surface.  The  diffuser  is  of  a  flat  cone 
shape  with  concentric  rings  to  additionally  diffuse 
the  light. 


Fig-.  7 

The  distribution  obtained  is  excellent  for  any 
general  illumination  in  industrial  service,  as 
shown  from  the  accompanying  curve  (Fig.  7) 
which  is  the  vertical  distribution  of  candlepower 
of  the  100  watt  multiple  Mazda  lamp  with  MM 
12"  diffuser,  form  "H"  holder:  (a)  clear  lamp; 
(£)  clear  lamp  with  MM  Diffuser;  (c)  bowl  frosted 
lamp  with  Mazda  mill  diffuser. 

Practically  all  of  the  light  flux  is  in  the  lower 
hemisphere  with  the  maximum  at  about  45°. 

The  following  sizes  are  available : 

12"  diameter        25  to  100  watt  Mazda- 
16"  100  to  250      ' 

21"  250  to  500      ' 

Holophane  D'Oh'er,  made  by  the  Holophane 
Works  of  the  General  Electric  Co. 

This  is  a  sheet  steel  reflector  of  two  finishes: 
(1)  Mat  aluminum  interior  finish  with  green  paint 
exterior;  (2)  Porcelain  enamel  inside  and  out. 

The  porcelain  enamel  has  these  advantages  ; 
it  is  more  readily  cleaned  resists  acid  fumes  and 
heat,  gives  good  service  in  the  open  and  is  a 
slightly  better  reflecting  surface  than  the  alu- 
minum. The  enameling  of  both  the  Mazda  Mill 
Diffuser  and  the  Holophane  D'Olier  reflector  is 


heavy  and  the  metal  rigid  so  that  there  is  no 
liability  of  the  porcelain  being  chipped  off  if  hit 
accidently  by  the  operatives. 

The  Holophane  D'Olier  reflector  is  bowl 
shaped,  made  to  give  two  distributions  with  alu- 
minum finish,  namely,  extensive  and  intensive, 
and  for  sizes  of  lamps  from  25  to  500  watts. 
The  enamel  finish  is  made  to  give  the  extensive 
distribution  only. 


Fig. 


The  above  curve  (Fig.  8)  shows  the  distribu- 
tion of  the  aluminum  finish  intensive  100  watt 
D'Olier  reflector  with  100  watt  Mazda:  (a)  bare 
clear  lamp:  (£)  clear  lamp  with  Holophane 
D'Olier  reflector;  (c)  bowl  frosted  lamp  with 
Holophane  D'Olier  reflector. 

The  D'Olier  reflector  is  also  made  in  the  alu- 
minum finish  in  the  form  of  an  angle  reflector, 
15-30-45  and  90°  for  use  in  localized  machine  light- 
ing with  the  smaller  wattage  Mazda  lamps. 

Decorative.  The  Holophane  Prismatic  reflector 
is  made  by  the  Holophane  Works  of  the  General 
Electric  Co.  This  reflector  is  typical  of  the  best 
prismatic  glass  reflectors,  and  is  applicable  for 
use  in  offices,  stores,  dwellings,  etc. 

This  reflector  is  of  a  scientific  design,  the  prisms 
being  carefully  calculated  to  direct  the  light  in 
the  required  directions  to  give  any  desired  dis- 
tribution, which  makes  it  the  most  efficient  dec- 
orative reflector  on  the  market.  For  distribution 
curves  of  these  reflectors  see  pages  31,  32  and  33. 

The  side  prisms,  besides  redirecting  the  light, 
serve  as  a  diffusing  medium,  and  allow  a  small 
portion  of  the  light  to  pass  through  and  illuminate 
the  ceiling  and  side  walls. 

The  standard  line  of  Holophane  reflectors  is 
made  to  give  extensive,  intensive,  and  focus- 

30 


Fig.  9 

Mazda  Lamps.    25,  40  and  60-watt,  100-130  volt, 
Bowl-frosted,  with  Intensive  Reflectors. 


Fig.  10 

Mazda  Lamps.    25,  40  and  60-watt,  100-130  volt, 
Bowl-frosted,  with  Extensive  Reflectors. 

31 


.   Fig.  11 

Mu/,da  Lamps.    25.  40  and  60-watt,  100-130  volt, 
Bowl-frosted,  with  Focusing-  Reflectors. 


Fig.  12 

Mazda  Lamps.    100,  150  and  250-watt,  100-130 
volt,  Bowl-frosted,  with  Intensive  Reflectors. 

32 


Fig.  13 

Mazda  Lamps.    100,  150  and  250-watt,  100-130 
volt,  Bowl-frosted,  with  Extensive  Reflectors. 


Fig.  14 

Mazda   Lamps.     100,  150  and  250-watt,  100-130 
volt*  Bowl-frosted,  with  Focusing  Reflectors. 

33 


ing  distribution,  in  sizes  from  25  to  500  watts.  A 
large  variety  of  spheres,  hemisperes.  reflector 
bowls,  stalactites,  and  ornamental  reflectors  for 
store  and  residence  use  are  also  made,  but  space 
does  not  permit  listing  them  here. 

Veluria  Reflectors,  made  by  the  Holophane 
Works  of  the  General  Electric  Co.,  are  typical  of 
opalescent  decorative  reflectors.  They  are  made 
the  of  opal  glass,  and  in  two  types,  the  bowl  and 
flared . 

Opalescent  glass  reflectors  are  particularly 
suited  for  residences,  etc.  where  the  artistic  effect 
is  more  important  than  the  actual  illuminating 
efficiency.  Fig.  15  shows  the  distribution  of 
the  bowl  shaped  100  watt  Veluria  reflector, 
with  a  100  watt  Mazda  lamp,  (a)  clear  lamp  ;  (b) 
clear  lamp  with  Veluria  reflector;  (c)  bowl 
frosted  lamp  with  Veluria  reflector. 


Fig.  15 

As  will  be  seen,  a  considerable  portion  of  the 
light  is  not  reflected  downward  but  is  diffused 
through  the  reflector  and  serves  to  illuminate 
the  side  walls  and  ceiling. 

The  Veluria  reflector  is  made  in  the  following 
finishes:  smooth  interior  and  roughed  exterior; 
smooth  exterior  and  roughed  interior ;  roughed 
interior  and  roughed  exterior :  smooth  interior 
and  exterior  roughed  with  design  etched  upon  it. 

Mazda  Monohix.  These  area  decorative  art 
glass  reflector  made  in  various  shapes  and  sizes 
to  accommodate  thehigherwattageMazda  lamps. 
They  are  particularly  adaptable  for  the  larger 
rooms  in  residences,  offices,  and  the  higher  class 
stores.  Various  types  of  distribution  can  be  ob- 
-  tain ed, depending  upon  the  shape  of  the  reflector. 
It  is  made  for  both  the  direct  and  semi-indirect 
systems  of  illumination,  and  is  exceedingly 
ornamental. 

34 


Distribution  curves  of  any  combinations  of 
lamps  and  reflectors,  or  other  information,  may 
be  obtained  from  the  General  Sales  Office  of  the 
Edison  Lamp  Dept.,  General  Electric  Co.,  Har- 
rison, N.  J. 

Miniature  Lamps 

The  subject  of  miniature  lamps  covers  a  wide 
range  of  uses  for  which  the  various  lamps  coming 
under  this  heading  are  employed.  The  field  of 
decorative  lighting  demands  the  use  of  various 
sizes  of  Miniature  lamps  to  bring  out  the  effects 
in  harmony  with  the  decorations  with  which 
they  are  used.  Churches,  libraries  and  resi- 
dences are  made  more  cheerful  by  the  soft  glow 
of  candelabra  lamps.  At  Christmas  time  the 
house  and  Christmas  tree  are  safely  and  artis- 
tically decorated  with  various  colored  lamps. 
Dentistry  and  surgery  make  use  of  the  extreme- 
ly small  lamps  which  may  be  inserted  in  incisions, 
furnishing  light  where  it  is  impossible  to  direct 
light  rays  from  any  other  source.  The  small 
battery  capacity  of  these  lamps  makes  their  use 
possible  under  all  conditions.  The  United  States 
Government  makes  use  of  a  great  number  of 
miniature  lamps  in  various  instruments,  and  in 
the  sighting  of  large  guns.  Telephone  switch- 
boards are  equipped  with  small  lamps,  by  means 
of  which  the  operator  is  signalled  by  the  sub- 
scriber. In  short,  the  Miniature  lamp,  in  some 
shape  or  style,  meets  almost  every  demand  in  the 
field  of  small  lighting. 

General  Battery  Lamps 

Mazda  General  Battery  lamps  are  made  for  use 
primarily  on  battery  circuits,  but  they  may  be 
used  on  any  low  voltage  circuit,  or  in  series  on 
circuits  of  standard  voltage. 

Novelty  Battery  Lamps 

Mazda  Novelty  Battery  lamps  are  used  with 
dry  batteries  in  all  kinds  of  ornamental  and 
portable  lighting  devices.  The  Mazda  filament 
emits  very  little  heat,  gives  a  very  brilliant  light 
and  requires  but  little  battery  capacity.  These 
characteristics  make  it  especially  desirable  for 
all  the  lighting  devices  in  which  the  Novelty 
Battery  types  are  employed. 

Lamps— 20  Volts  and  Below 

The  low  voltage  besides  permitting  the  use  of 
a  short  sturdy  filament  in  the  low  volt  lamp,  pro- 
vides for  the  production  of  low  candle-power  with 
low  wattage  consumption. 

Automobile  and  Electric  Vehicle  Lamps. 

Electric  lamps  have  two  important  advantages 
for  Automobile  Lighting ;  safety  and  conven- 

35 


ience.  The  fact  that  the  foremost  car  manufac- 
turers are  equipping  their  cars  with  electric  lights 
is  proof  that  these  advantages  are  real  and  not 
fancied.  With  the  electrically  equipped  car  there 
is  no  annoyance  in  lighting  lamps  and  no  fire 
risk  from  high  pressure  gas.  A  better  focus  can 
be  obtained  with  the  electric  lamp,  as  the  exces- 
sive heat  of  a  gas  flame  prohibits  the  placing  of 
same  deep  enough  in  the  reflector  to  use  the 
greater  part  of  the  light,  while  the  low  heat 
of  the  electric  light  permits  its  being  set  back  in 
a  deep  reflector.  Furthermore,  the  electric  head- 
light is  concentrated  into  practically  a  po.'nt  at 
the  focal  center  and  remains  steady  and  in  focus, 
as  it  cannot  flicker  or  be  blown  out  of  focus  by 
the  wind.  The  interior  equipment  of  a  limousine 
shows  the  convenience  and  beauty  of  electric 
lamps  as  applied  to  auto  lighting. 

The  standard  voltage  adopted  by  manufac- 
turers for  auto  lighting  is  6  volts.  This  low 
voltage  permits  the  use  of  a  short  metallic  fila- 
ment of  a  comparatively  large  cross  section. 
The  side  lights  are  supplied  in  G-8  and  G-10  bulbs 
in  candle-powers  of  3,  4  and  6,  and  of  3,  6  and  8 
respectively.  In  the  P-8  and  P-9  bulbs,  also  used 
as  side  lights,  the  candle-powers  are  4  and  6,  and 
6  and  8.  The  rear  lights  are  furnished  in  G-8  bulbs 
1-3^  candle-power,  and  in  G-6  bulbs  in  l-#,  2  and  3 
candle-power.  The  headlight  is  equipped  with  a 
vertical  coil  filament  and  furnishes  9, 12, 15  and  18 
candle-power  in  the  G-12  bulb,  and  15, 18.  21  and  24 
candle-power  in  the  G-16->£  bulb.  It  has  an  effi- 
ciency of  1  watt  per  candle.  The  standardized 
focal  length  for  parabolic  reflectors  is  \"  and  the 
filament  mounted  in  the  G-12  or  G-16-#  bulb 
meets  this  requirement.  These  lamps  are  fur- 
nished either  with  a  standard  candelabra  base  or 
with  a  bayonet  candelabra  base.  The  latter  is 
more  generally  used,  and  is  recommended  be- 
cause there  is  no  possibility  of  its  jarring  out  of 
the  socket. 

For  electric  vehicle  service  the  General  Elec- 
tric Co.  offers  a  complete  line  of  electric  vehicle 
lamps,  ranging  from  21  to  65  volts  in  G-16%  (2Vte  ' 
diatn.),  and  21  to  90  volts  in  G-18&  (25/i6//  diam.) 
round  bulbs.  These  are  made  in  15  and  25  watt 
sizes  and  operate  at  an  efficiency  of  1.23  W.  P.  C. 

Current  Supply  Systems 

There  are  three  distinct  systems  in  general  use 
for  supplying  energy;  the  storage  battery,  the 

36 


generator  and  storage  battery,  and  the  magneto 
system.  With  the  storage  battery  system,  the 
six  volt  battery  is  in  general  use,  although  elec- 
trically driven  machines  operate  the  lights  on 
various  voltages,  according  to  the  make  of  the 
machines.  A  Ithough  it  is  not  practical  to  operate 
lights  on  ignition  batteries,  the  lighting  battery 
when  properly  equipped  can  be  used  for  the 
ignition.  With  such  a  system  it  is  good  practice 
for  the  wiring  to  be  such  that  the  headlights  can 
be  switched  off  and  the  side  lights  be  left  burning 
while  running  in  the  city,  and  vice  versa  when 
running  in  the  country. 

In  the  generator  and  storage  battery  systems 
the  battery  floats  on  the  line  and  furnishes  the 
energy  for  the  lights  when  the  car  is  at  a  stand- 
still or  running  at  a  speed  so  low  that  the  voltage 
would  otherwise  be  too  low  to  light  up  the  lamps. 
When  the  generator  voltage  falls  below  that  of 
the  battery  the  generator  is  disconnected  by  a 
disconnecting  switch,  making  it  impossible  for 
the  battery  to  discharge  and  run  the  generator 
as  a  motor. 

One  of  the  most  successful  types,  by  virtue  of 
an  ingenious  yet  simple  scheme  of  winding,  auto- 
matically regulates  the  current  irrespective  of 
speed  variations.  That  is,  when  the  lamps  are 
turned  on,  a  higher  current  output  from  the 
generator  itself  is  obtained.  When  the  lamps 
are  switched  off,  the  current  falls  off  to  a  safe 
charging  value  for  the  batteries.  The  field  is 
compound  wound,  and  is  surrounded  by  a  per- 
manent magnet  to  prevent  a  reversal  of  polarity. 
Provision  can  be  made  for  ignition  in  conjunction 
with  the  lighting  system.  The  generator  can  be 
driven  by  gear,  silent  chain  or  belt  drive. 

In  the  magneto  system  a  storage  battery  must 
be  used  as  an  auxilliary,  with  a  relay  or  hand 
operated  switch  to  throw  it  on  when  the  car  is 
not  running.  With  any  generating  or  battery 
system  it  is  necessary  to  have  the  smallest  pos- 
sible length  of  wire  between  the  source  of  energy 
and  the  lights,  since  with  so  low  a  voltage  a 
small  drop  means  a  big  per  cent,  of  the  original 
voltage. 

Any  argument  which  applies  to  the  lighting  of 
automobiles  by  electricity  applies  equally  well  to 
motor  boats  and  motor  cycles.  For  the  motor 
cycle  the  limited  space  gives  the  electric  head- 
light an  advantage  over  any  other  means  of 
illumination.  A  3"  X  3"  X  6",  2  volt,  20  ampere 
hour  battery  is  generally  used,  and  can  be  placed 
in  the  tool  box. 

Bulbs 

The  shape  of  the  bulb  of  the  regular  types  is 
designated  by  a  letter,  and  the  diameter,  in 
eighths  (pf  an  inch,  by  a  figure  following  this 
letter;  "P"  for  pear  shape,  V'G"  for  round  and 
"T"  for  tubular.  For  example  a  G-12  bulb  is  a 


round   bulb   \1A"  in  diameter;   a  G -6  bulb  is  a 
round  bulb  %"  in  diameter.    Besides  the  regular 
types  there  are  various  shaped  bulbs  for  decora- 
tive purposes  and  many  other  special  lamps. 
Bases 

The  standard  bases  for  miniature  lamps  are 
the  miniature  screw  b^se  and  candelabra  screw 
base.  The  former  is  W  in  diameter  and  7/i«" 
long,  with  14  threads  to  the  inch,  and  the  latter 
is  Vie"  in  diameter  and  1%2//  long,  with  10 
threads  to  the  inch.  The  Bayonet  Candelabra 
base  is  furnished  for  special  service,  such  as 
automobiles,  etc. 
Sockets  and  Shades 

A  large  line  of  shades  of  all  colors  is  supplied 
for  Miniature  lamps,  which  add  materially  to 
their  decorative  qualities.  Since  shade  holders 
for  Miniature  Candelabra  sockets  are  not  inter- 
changeable, the  style  wanted  should  always  be 
specified. 

Train  Lighting 

It  is  needless  to  dwell  upon  the  advantages  of 
electrically  lighted  trains.  Along  with  the  mod- 
ern steel  coaches  the  further  safety  of  electrical 
equipment  is  essential.  Other  than  immunity 
from  fire,  there  are  added  advantages  both  in 
convenience  and  in  appearance.  An  electrical 
equipment  permits  the  u^e  of.  berth-lights  and 
any  desired  distribution  of  units.  The  train  so 
equipped  with  means  for  making  travelling 
pleasant  has  in  itself  a  definite  advertising 
value.  The  Drawn  Wire  filament  of  the  Mazda 
lamp,  with  its  low  energy  consumption,  its 
strength,  and  its  adaptability  to  any  situation, 
has  solved  the  problem  of  scientific  and  eco- 
nomical train  lighting. 

The  round  bulb  has  been  generally  adopted 
as  a  standard  for  train  lighting,  as  this  type  har- 
monizes much  better  with  the  general  appear- 
ance of  the  car.  10,  15,  20  and  25  watt  Mazda 
lamps  are  supplied  in  the  G-18>2  round  bulbs, 
2-5/16"  in  diameter,  and  a  50  watt  lamp  in  the 
G-30  round  bulb,  3-%"  in  diameter.  10,  15, 
20  and  25  watt  lamps  are  also  supplied  in  either 
the  S-19  bulb,  2-3/8"  in  diameter,  or  the  S-17 
bulb,  2-1/8"  in  diameter.  A  40  watt  lamp  is 
supplied  in  the  S-19  bulb,  2-3/8"  in  diameter,  and 
a  50  watt  lamp  in  the  S-21  bulb,  2-5/8"  in  diam- 
eter. These  lamps  are  all  furnished  in  two 
ranges,  25  to  34  volts  and  50  to  65  volts.  At  pres- 
ent the  15  watt  Mazda  lamp  in  the  G-18-1/2  bulb 
is  generally  used  for  berth  lights,  although  the 
Gem  lamp  in  a  G-12  bulb,  1-1/2"  in  diameter  is 
sometimes  used  in  coaches  having  old  fixtures. 

The  Edison  Train  Lighting  lamps  are  furn- 
ished with  the  medium  screw  base,  except  the 
Gem  Berth  Light,  which  is  fitted  with  the  Can- 
delabra screw  base. 

Three  general  systems  for  supplying  current 


.ire  used  in  train  Hghting.    They  are  known  as 

he  "Head-End,"  "Straight  Storage"  and  "Axle 
Generator"  systems. 
Head-End  System 

The  Head-end  system  consists  of  a  complete 
power  plant,  including  a  steam  turbine-driven 

generator,  a  storage  battery  and  a  switchboard. 
The  generating  set  is  located  either  in  the  bag- 
gage car  at  the  front  of  the  train,  or  is  mounted 

m  the  locomotive.  When  installed  in  the  bag- 
gage car,  steam  is  supplied  from  the  locomotive 

;ither  by  a  direct  steam  line  or  through  the 

leating  system. 

The  battery  supplies  current  for  the  lights 
when  the  locomotive  is  disconnected  from  the 
train.  It  also  supplies  a  part  of  the  current 
\vhen  the  load  is  greater  than  the  capacity  of 
the  generator  set.  An  additional  battery  is  often 

nstalled  in  the  rear  car  so  that  the  rear  half  of 
the  train  will  not  be  in  darkness  in  case  an  extra 
car  is  placed  in  the  middle  of  the  train. 
The  Head-end  system  is  used  principally  on 

'solid  trains"  where  the  cars  are  kept  together 
throughout  the  entire  trip. 

Straight  Storage  System 

In  the  Straight  Storage  system,  storage 
batteries  are  used  alone,  one  for  each  car.  The 
cells  are  usually  arranged  in  two  sets  of  16  each, 
which,  when  connected  in  series,  give  a  voltage 
range  of  57  to  65  volts,  and  when  in  multiple,  a 
voltage  range  of  28  to  34  volts. 

With  the  straight  storage  system,  facilities  for 
charging  the  batteries  must  be  provided  at  the 
terminals. 

Axle  Generator  System 

The  Axle  Generator  system  consists  of  a  small 
generator  on  each  car,  usually  mounted  on  the 
truck  frame,  and  driven  from  the  car  axle  by  a 
belt  or  chain.  A  storage  battery  is  also  pro- 
vided for  each  car  to  furnish  light  when  the  car 
is  not  moving. 

In  order  to  prevent  the  battery  from  feeding 
back  into  the  generator  when  the  train  is  run- 
ning at  low  speed,  an  automatic  switch  is  used 
which  disconnects  the  generator  from  the  bat- 
tery when  the  voltage  of  the  generator  is  lower 
than  that  of  the  battery.  This  automatic  switch 
also  connects  the  generator  to  the  battery  when 
the  voltage  of  the  generator  rises  to  the  normal 
value.  It  is  usually  designed  to  connect  in  at 
train  speeds  of  about  15  miles  per  hour. 

To  prevent  the  generator  voltage  from  rising 
to  an  excessive  value  when  the  train  is  running 
at  speeds  higher  than  the  "cutting-in"  speed,  a 
regulating  device  is  used,  consisting  of  a  vari- 
able resistance  inserted  in  the  field  of  the  gen- 
erator, or  a  separately  driven  generator  which 


either  bucks  or  boosts  the  main  generator  field. 

An  automatic  device  is  also  used  to  maintain 
the  polarity  of  the  wires  from  the  generator  to 
the  battery  when  the  direction  of  the  car's  mo- 
tion is  reversed. 

Automatic  variable  resistances  are  used  in 
series  with  the  lamp  circuits  to  maintain  a  more 
nearly  constant  voltage  at  the  lamps.  This  re- 
duces the  lamp  renewal  cost  by  preventing  ex- 
cessive voltage  on  the  lamps,  and  furnishes 
steady  illumination. 


Sign  Lighting 

Electric  Sign  Lighting  is  simply  a  part  of  the 
immense  advertising  field,  and  should  be  so  con- 
sidered. It  should  be  borne  in  mind  by  the 
merchant,  the  sign  maker  and  the  central  sta- 
tion that  an  electric  sign  is  first,  last  and  always 
an  advertisement,  and  its  ultimate  success  de- 
pends to  what  degree  these  facts  are  borne  in 
mind. 

Some  merchants  seem  to  have  the  impression 
that  an  electric  sign  is  expensive  advertising. 
Nothing  is  furtner  from  the  truth.  When  con- 
sidered strictly  as  an  advertisement  and  figured 
on  a  per  capita  basis,  electrical  advertising  is  the 
cheapest,  as  well  as  the  most  effectual  method 
of  reaching  the  public.  National  advertisers  are 
beginning  to  realize  this  and  are  erecting  large 
spectacular  displays  in  the  principal  cities  of  this 
country. 

As  compared  with  other  methods  of  advertis- 
ing the  electric  sign  has  the  following  advan- 
tages: 

It  works  both  night  and  day. 

It  has  the  virtue  of  continual  repetition. 

It  costs  less  per  capita  than  any  other  method 
of  advertising. 

It  is  brief,  concise  and  right  to  the  point. 

The  impression  produced  is  a  lasting  one. 

No  turning  of  pages. 

No  irrelevant  matter. 

Costs  nothing  to  read  it. 

Read  by  all  classes  of  people. 

Kindly  bear  in  mind  that  it  is  not  the  object  of 
the  electric  sign  to  supplant  either  newspaper 
or  magazine  advertising,  as  these  branches  of 
advertising  are  closely  related,  and  in  order  to 
get  the  best  results  all  should  be  used  in  con- 
junction with  each  other.  The  story  is  told  in 
detail  in  magazines  and  newspapers,  and  the 
spectacular  electric  sign  follows  with  its  flashing 
presentation  of  the  trademark  or  name  of  the 
merchant. 

To  produce  the  best  results,  signs  should  be 
carefully  constructed,  for  good  material  and 
workmanship  are  very  essential.  The  sign 
should  be  erected  in  such  a  way  as  not  only  to 

40 


3  oo  «o  Tf  e*  o  a 

2i?"s3ss^s 


UJ    .S 


.appear  safe  but  also  to  be  safe.  The  signs  built 
by  the  successful  companies  are  designed  on  this 
principle,  having  a  higher  factor  of  safety  than 
would  appear  to  be  necessary,  so  that  a  failure 
of  any  part  of  the  sign  is  practically  impossible. 

Sign  Lamps 

The  Mazda  Sign  lamp  situation  has  been  won- 
derfully improved  by  the  addition  of  two  new 
lamps.  The  General  Electric  Company  is  now 
manufacturing  10  watt,  100  to  130  volt,  and  5 
watt,  50  to  65  volt  Mazda  Sign  lamps.  The  ad- 
dition of  these  two  new  lamps  makes  the  sign 
lamp  schedule  complete,  and  there  is  no  logical 
reason  why  any  merchant  should  continue  to 
use  the  inefficient  carbon  lamps.  The  use  of  the 
Mazda  lamps  insures  more  light  and  better  light 
for  less  expense  than  the  Carbon  lamps.  See 
Table  10  for  a  complete  list  of  Mazda  Sign  lamps. 


10.    TECHNICAL    DATA   COVERING  THE  COM- 

PLETE SCHEDULE  OF  MAZDA  SlGN  LAMPS. 


ltage 


10  -13 
10  -13 
10  -13 
50  -65 


100-130  10 


.33 
1.33 
1.33 
1.5 
1.5 


1.8  120001100 1    S-14 
3.8J200-J100      S-14 
3.8  2000:100 
3.3  2000J100 
6.7  !2000!100 


S-14 
S-14 


Std. 
Std. 
:and. 


As  the  10-13  volt  sign  lamps  are  made  in  1/2 
volt  steps,  the  voltage  of  the  lamps  to  use  would 
be  the  nearest  1/2  volt  obtained  by  dividing  the 
circuit  voltage  by  10.  As  an  example,  suppose 
the  circuit  voltage  in  a  particular  case  is  113;  by 
dividing  113  by  10  we  get  11. 3,  and  hence  we  should 
use  11.5  volt  lamps  in  this  case.  With  the  50-65 
volt  and  100-130  volt  lamps,  the  voltage  to  be 
ordered  should  be  obtained  by  testing  the  vol- 
tage directly  at  the  lamp  sockets  In  case  of 
voltage  fluctuation  the  maximum  value  should 
be  used. 

It  has  been  demonstrated  time  and  time  again 
that  when  operated  properly  Mazda  Sign  lamps 
give  satisfactory  results.  In  order  to  avoid  mis- 
understanding in  the  future  each  method  of 
wiring  will  be  taken  up  separately. 

Mazda  Sign  wiring,  as  experienced  by  the  Cen- 
tral Station  and  merchant,  may  be  divided  into 
two  broad  classes: 

First,  Cities  having  direct  current. 

Second,  Cities  having  alternating  current. 

On  the  opposite  page  is  given  in  tabulated  form 
the  methods  of  wiring  and  types  of  lamps  to  use 
-on  direct  current. 

42 


For  Cities  Having  Direct  Current 


Size  of  Sign    Voltage    Wattage 


Lamp 
to  Order 


Under  100  10-13  2.5,5,  10  in  series  Series 

Over     100  10-13  2.5,5,  Multiple  series  Series 

Any  number  50-65  5  2  in  series  Series 

"          "  100-130  10  Multiple  Multiple 


10  in  Series 

It  will  be  noted  in  the  above  table  that  the 
series  method  of  wiring  with  10  lamps  in  series 
(Fig.  16)  is  only  recommended  where  the  sign  con 
tains  less  than  100  lamps.  Under  no  condition 
should  a  sign  containing,  say  300  or  400  lamps  be 
wired  in  straight  series,  as  unsatisfactory  per- 
fcrmancewill  probably  result.  It  is  recommended 
that  in  every  case  10  lamps  be  wired  in  each  series, 
the  voltages  of  the  lamp  being  one-tenth  of  the 
circuit  voltage.  As  the  same  current  flows 
through  all  the  lamps  in  each  series,  it  is  neces- 
sary that  the  lamps  be  selected  for  amperes.  This  is 
done  by  the  lamp  manufacturers,  and  all  lamps  so 
selected  have  an  additional  label  reading  SERIES 
BURNING.  Do  not  operate  lamps  of  different 
manufacture  in  the  same  series,  because  the 
different  manufacturers  select  their  series  lamps 
according  to  different  schedules,  and  hence  by 
mixing  them  unsatisfactory  performance  will 
result. 


Fig.  16 

Multiple    Series 

When  a  sign  contains  more  than  100  lamps, 
and  it  has  been  decided  to  use  10-13  volt  lamps, 
it  is  recommended  that  they  be  wired  in  mul- 
tiple series  (Fig.  17)  with  10  multiple  banks  con- 

43 


nected  in  series.  If  it  is  decided  to  wire  less  than 
100  lamps  in  this  manner  it  is  recommended  that 
enough  resistance  be  inserted  to  make  the  total 
resistance  equal  to  that  of  100  lamps.  As  series 
lamps  are  selected  for  volts  and  amperes,  it  is 
evident  that  they  should  be  used  for  this  class  of 
service  and  the  order  should  so  specify. 


-o 

0< 

K 

-0 

o- 

-0 

-o-> 

-o 

•o 

•0 

-o^ 

o- 

-0-. 

-o 

o- 

-0 

-o 

-CH 

-On 

-o- 

-o 

-o- 

-o 

-o- 

OH 

-o 

-o- 

•o- 

-o 

-o- 

-o- 

-0 

•On 

-0 

-o-1- 

-o-  -o  -o 
-o-  -o  -o-   -o- 


•-o-   - 
-o   - 


Fig.  17 

When  the  lamps  are  so  wired  that  the  failure 
of  one  lamp  in  a  multiple  bank  causes  the  re- 
maining lamps  to  be  operated  at  an  excess  volt- 
age, it  is  suggested  that  all  burn  outs  be 
promptly  replaced.  Therefore,  when  a  sign  is 
wired  in  this  manner  it  should  be  easily  access- 
ible so  that  any  lamp  which  has  failed  can  be  re- 
placed promptly  and  conveniently. 

50-65  Volt,  5- Watt  Mazda  Lamp 

This  lamp  has  recently  been  standardized  and 
it  is  a  long  step  forward  in  the  series  sign  lamp 
proposition  on  direct  current.  These  lamps  may 
be  wired,  either  two  in  series  (Fig.  18)  or  in  mul- 
tiple series  (Fig.  19.)  When  wired  two  in  series,  it 


Fig.  18 


is  suggested,  that  the  lamps  be  staggered  so  that 
the  failure  of  one  lamp  will  not  throw  out  two  ad- 
jacent lamps.  In  the  case  of  a  double  face  sign  it  is 
recommended  that  the  lamps  on  each  side  be 
wired  in  multiple  and  the  two  sides  be  con- 
nected in  series.  In  this  way  we  get  a  condition 
of  operation  which  is  practically  similar  to 

44 


straight  multiple,  as  when  approximately  50 
amps  are  used  on  a  sign,  the  failure  of  one  lamp 
will  not  unbalance  the  circuit  to  any  appreciable 
extent. 


Service  Wires 


Fig.  19 


100-130  Volt,  10  Watt,  Mazda  Lamp 

This  new  sign  lamp  makes  it  possible  to  wire 
the  signs  in  straight  multiple,  (Fig.  20)  this  be- 
ing the  most  simple  and  satisfactory  method  of 
wiring  in  practice.  This  lamp  makes  it  possible 
to  eliminate  transformer  expense,  and  thus 
helps  to  offset  the  slightly  higher  renewal  cost 
of  the  lamps.  It  is  possible  to  replace  any  exist- 
ing 30-watt  or  20-watt  Carbon  lamp  by  this  lamp, 
without  any  rewiring,  to  show  a  material  sav- 
ing to  the  customer,  and  at  the  same  time 
greatly  improve  the  appearance  of  his  sign. 


o- 

2 

SL 

5 

5 

§ 

^> 

o- 

G- 

4 

5 

5 

5 

5 

§ 

Fig.  20 
For  Cities  Having  Alte  mating  Current 

11.  TABLE  SHOWING  THE  LAMPS  AND  METHODS 
OF  WIRING  TO  USE  IN  CITIES  HAVING  ALTER- 
NATING CURRENT. 


SizeofSign 

Lamps 

Method  of 
Wiring 

Lamp  to 
Order 

Voltage 

Wattage 

Any  Size 
Any  Size 
Any  Size 

10  -13 
50  -65 
100-130 

2.5,5 
5 
10 

Multiple,  trans, 
two  in  series 
Multiple 

Multiple 
Series 
Multiple 

10-13  Volt  Lamps 

Since  the  multiple  method  (Fig.  20)  of  oper- 
ating lamps  is  always  the  best,  it  is  recom- 
mended that  a  transformer  be  used  whenever 


alternating  current  is  available.  The  trans- 
former expense  is  justified  since  the  best  possi- 
ble performance  is  secured  by  its  use. 

50-65  Volt,  5  Watt  Lamp 

This  lamp  will  operate  just  as  satisfactorily 
on  alternating  current  as  on  direct  current,  and 
the  same  methods  of  wiring  should  be  employed 
in  both  cases. 

100-130  Volt,  10  Watt  Lamp 

This  lamp  can  be  operated  on  alternating  cur- 
rent with  the  same  success  as  on  direct  current. 
Its  use  simplifies  both  the  wiring  and  operation. 

Wiring 

For  low  voltage  Mazda  Sign  lamps  the  wiring 
must  be  such  that  the  voltage  drop  does  not  ex- 
ceed a  certain  definite  amount,  and  that  the 
Fire  Underwriters'  Rules  are  not  violated.  Ac- 
cording to  the  specifications  of  the  National 
Board  of  Fire  Underwriters  not  more  than  1320 
watts  shall  be  dependent  upon  the  final  cut-out. 
In  some  cases,  however,  the  municipal  rules 
allow  only  660  watts,  and  this  ruling  must  be 
observed  and  the  wiring  governed  accordingly. 
Below  is  a  table  which  shows  the  carrying  ca- 
pacity of  wires  as  approved  by  the  National 
Board  of  Fire  Underwriters.  It  is  seen  from 
this  Table  that  with  low  voltage  Mazda  lamps 
the  carrying  capacity  of  the  wires  is  the  govern- 
ing feature. 

12.    CARRYING  CAPACITY  OF  WIRES 


B  &S 
Gauge 

Rubber 
Insula- 
tion 
Amperes 

No.Swatt 

10-13 
Volt 
Lamps 

No  5  watt 
50-65 
Volt 
Lamps 

No.  10  watt 
100-130 
Volt 
Lamps 

14 
12 
10 
8 
6 
5 
4 
3 
2 
1 
0 

12 
17 
24 
33 
46 
54 
65 
76 
90 
107 
127 

27 
38 
54 
75 
104 
122 
147 
172 
204 
242 
J 

127 
181 
256 

I 

1 

t  Exceeds  the  1320  watts  as  allowed  by  Na- 
tional Board  of  Fire  Underwriters. 

With  the  10-13  volt  lamps  it  is  essential  that  the 
voltage  drop  in  all  cases  be  less  than  %  volt. 
Table  13  gives  the  number  of  lamps  which  can  be 
used  on  the  four  different  sizes  of  wire  when  the 


13.    SHOWING  RELATION  BETWEEN   NUMBER 
OF  LAMPS,  SIZE  OF  WIRE,  SPACING  AND  VOLTAGE 

DROP. 


Spacing 
of  Lamps 
in  Inches 

Size  of  Wire  (B  &  S) 

14         .12         10          8 

6 
8 
10 
12 
16 
20 

64* 
55 
47 
42 
38 
33 
29 

92* 
70 
60 
54 
49 
42 
38 

125* 

88 
75 
68 
62 
54 
48 

159* 
112 
97 
86 
79 
68 
61 

Number 
of 
Lamps 

14.    NUMBER  OF  LAMPS,  SIZE  AND  LENGTH  OF 

FEEDERS  , 


Combined 

length  of  pair 

of  feeders. 


Size  of  Feeder  (B  &  S) 
10      8       6       4       2 


3 

64* 

92* 

130* 

184* 

262* 

4 

50 

77 

125 

184* 

262* 

5 

40 

62 

100 

158 

254 

6 

33 

53 

84 

135 

210 

Number 

8 

25 

40 

63 

101 

160 

of 

10 

20 

31 

50 

79 

127 

Lamps 

15 

13 

21 

33 

53 

85 

20 

10 

15 

25 

39 

63 

30 

7 

10 

17 

26 

42 

*  This  limit  imposed  in  order  not  to  exceed  the  safe  carrying 
capacity  of  weather-proof  wire. 

With  the  50-65  volt,  5  watt,  and  100-130  volt,  10 
watt  lamps,  since  the  amperage  is  very  small  the 
governing  feature  will  be  the  limit  of  1320  watts 
imposed  by  the  National  Board  of  Fire  Under- 
writers. 
Sign  Lighting:  Transformers. 

The  General  Electric  Company  has  developed 
a  complete  line  of  transformers  for  reducing  the 
circuit  voltage  to  that  of  Mazda  sign  lamps.  The 
transformation  ratio  is  10  to  1  and  20  to  1 .  and  con- 
sequently with  a  primary  voltage  averaging  110, 
11  volt  lamps  should  be  used  and  with  primary 
voltage  of  120,  12  volt  lamps  should  be  used,  etc. 
These  transformers  are  made  in  four  standard 
sizes,  as  shown  in  Table  15. 

As  the  secondary  can  be  connected  for  either 
two  or  three  wire  service,  the  transformers  can, 
therefore,  be  applied  to  any  sign  without  neces- 
sitating a  change  in  wiring. 

47 


15.    G.  E.  Sign  Lighting  Transformers. 


Capacity 
Waits 

Capacity 
5-watt 
Lamp 

Wall 
Space 
Inches 

Depth 
Inches 

Net 
Weight 
Pounds 

Catalog 
Number 

250 
500 
1000 
2000 

50 
100 
200 
400 

7x6* 

8x8 
9x9 
lOKxlO 

5% 
7K 

9 
10 

30 
45 
70 
100 

76676 
76678 
76680 
76683 

Flashers. 

The  flasher  has  three  advantages;  it  gives 
movement,  which  attracts  attention,  enables  one 
to  secure  spectacular  effects,  and  reduces  the 
amount  of  current  necessary  to  operate  a  given 
sign.  To  prevent  arcing  and  also  because 
most  flashers  are  designed  to  operate  on  110  volts, 
it  is  recommended  whenever  possible  that  the 
flasher  be  placed  on  the  service  side  of  the 
transformer.  However  the  simple  on  and  off 
flashing  sign  is  the  only  type  that  can  be  so  ar- 
ranged because  the  several  circuits  of  a  com- 
plicated sign  must  be  brought  together  at  the 
flasher  and  cannot  be  united  in  the  transformer 
on  the  way. 

In  Table  16  we  have  given  the  various  kinds  of 
flashing  effects  with  the  corresponding  possible 
methods  of  wiring  on  either  direct  or  alternating 
current.  The  type  of  lamp  which  can  be  used  in 
order  to  produce  these  flashing  effects  is  shown 
in  the  last  column. 

16.  TABLE  SHOWING  THE  POSSIBLE  SYSTEMS 
OF  WIRING  AND  LAMPS  TO  USE  FOR  VARIOUS 

FLASHING  EFFECTS  : 

Flashing 
Effect 

fMult. 
A.C.    | 

or    J  Mult.  Series 
rj)  c    I  Ten  in  series 

One  line  I  (  Two  " 

atatimej   A.C. 
Flashing 
Effect 
Script 
Spelling 
Fountain 


Current 


Wiring 


Steady 
Burning 

On  and 
Off 


Lamps 

110  V.  Mazda 


10  V. 
10  V. 
55V. 
"  Mult,  with  Trans.  10  V. 


Current 


Wiring 


Lamps 


Multiple      110  V.Mazda 
I  A.C.    , 

j  Multiple 
'   A.C.   ^with Trans.  10  V.  Mazda 


1    D.C. 

or 

_  A.C. 
Rat  Chaser 
Falling  Water  . 
Lightning         J 

Tn  order  to  estimate  approximately  the  number 
of  lamps  which  will  be  required  for  any  sign,  the 
following  table  is  given  which  shows  the  average 
number  of  sockets  for  different  sizes  of  letters 

48 


Average  Number  Sockets  for  Different 
Size  Letters 


12"-. 
14  "... 
16  "- 
24  ".. 
36"... 
48"-., 
60"... 
72"... 
84"... 


..20 

-.24 


-.27 


96" 32 

108" 36 

120" 1 39 

In  Special  designs  a  space  of  5  "  between  cen- 
ters of  sockets  can  be  used  for  estimating  the 
number  of  receptacles. 


1    2    3    4    5    6    7    8    9  10  11  12 
Rate  per  Kw.-hr.  in  Cents 


Fig.  21 

Fig.  21  shows  the  approx.  total  operating  costs 
?n\corresP°ndin8:  cart>on  and  Mazda  sign  lamps 
The  decided  economy  of  the  Mazda  lamps  is 
clearly  shown.  These  curves  are  based  on  stand- 
ard package  prices  in  effect  June  1,  1912. 

49 


Street  Lighting 

During  the  last  few  years  remarkable  ad- 
vances have  been  made  in  the  standard  of 
illumination  required  for  street  lighting.  The 
introduction  of  Mazda  Street  Lighting  Lamps 
has  undoubtedly  been  one  of  the  most  note- 
worthy advances  along  this  line.  With  the  in- 
creased economy  and  effectiveness  insured  by 
their  use,  the  benefits  of  electric  street  lighting 
are  now  practically  applicable  to  all  classes  of 
service  in  either  large  or  small  cities.  They  have 
for  the  first  time  made  it  commercially  possible 
to  operate  satisfactorily  both  arc  and  incandes- 
cent units  in  series  on  the  same  circuit,  thus  pro- 
viding the  most  flexible  and  efficient  system  of 
street  lighting  ever  devised.  This  system  allows 
a  wide  selection  of  candle  power  sizes  so  that  by 
distributing  both  Mazda  and  Arc  Lamps  where 
they  will  do  their  best  work,  a  very  effective  and 
economical  arrangement  can  be  obtained,  which 
eliminates  much  of  the  dissatisfaction  inherent 
in  former  systems  of  lighting.  Moreover  the 
conditions  of  the  present  day  differ  greatly  from 
those  of  the  past ;  greater  crowds  are  on  the  street 
in  the  evening;  high  speed  vehicles  are  more 
generally  used;  the  commercial  value  of  good 
lighting  is  realized  by  a  larger  per  cent,  of  busi- 
ness men ;  the  scientific  principles  of  streetlight- 
ing  are  better  understood,  and  above  all  there 
has  been  a  decided  gain  in  the  efficiency  and 
economy  of  lighting  units.  These  conditions  re- 
quire that  both  city  and  country  roads  be  much 
better  illuminated  than  was  formerly  possible 
•without  an  excessive  expenditure  of  money. 

The  problem  of  meeting  the  above  conditions 
is  solved  by  the  Series  Mazda  system.  The  ad- 
vantages <>f  this  system  may  be  briefly  summar- 
ized as  follows : 

1.  The  Series  Mazda  system  effects  a  great 
saving  in  copper  and  energy  transmission  losses 
on  account  of  its  comparatively  high  line  voltage. 

2.  The  Series  Mazda  system  has  a  very  low 
maintenance  cost  per  unit  on  account  of  the  ex- 
tremely long  life  of  the  Mazda  lamp,  its  high 
energy  efficiency  and  the  very  slight  amount  of 
attention  required  during  life. 

3.  Series  Mazda    lamps    will    burn    under    a 
great  variety  of  conditions  and  are  absolutely 
unaffected  by  external  surroundings  or  weather 
conditions 

4.  Series  Mazda  lamps  are  made  for  many 
different  current  strengths,  thus  allowing  the 
selection  of  that  value  of  current  which  is  most 
economical  under  the  local  generating  and  trans- 
mission conditions. 

5.  Series  Mazda  lamps  are  made  in  many  dif- 
ferent sizes,  and,  as  all  operate  at  a  high  effi- 
ciency, that  size  unit  can  be  selected  which  will 
give  the  desired  amount  of  light  most  economic. 


ally,  or  where  the  appropriations  for  street 
lighting  increase  slowly,  the  standard  of  illumi- 
nation can  be  increased  accordingly. 

6.  The  Series  Mazda  system   allows  several 
different  size  units  to  be  connected  to  the  same 
circuit,  and  an  easy  method  of  changing  either 
temporarily  or  permanently  the  amount  of  light 
at  any  spot. 

7.  Series  Mazda  lamps  have  a  low  intrinsic 
brilliancy  and  thus  reduce  glare  to  as  low    a 
value  as  is  compatible  with  economy. 

8.  A  Series  Mazda  system  permits  standard' 
ization    of    equipment,    interchangeability     of 
parts,  and  lighting  of  an  entire  city  from  the 
same  or  similar  circuits. 

9.  The  Series  M  azda  system  offers  a  simplicity 
and  ease  of  operation  and  control  unsurpassed 
by  any  other  system. 

10.  The  Series  Mazda  system  utilizes  to  the 
highest  degree  all  the  light  rays  from  the  lamp 
units,  even  when  the  streets  are  narrow,  crooked, 
hilly  or  lined  with  shade  trees. 

11.  The  Series  Mazda  lamps  when  equipped 
with  radial  wave  reflectors  increase   by  about 
25%  the  maximum    intensity    of   light    at   the 
angles  near  the  horizontal,  thus  throwing  the 
greatest  amount  of  light    out   to    the    distant 
points. 

12.  The  Series  Mazda   lamps    have    a   color 
value  very  near  to  that  of  daylight,  thus  giving 
objects  their  normal  appearance. 
Equipment 

With  a  Series  Mazda  system  all  the  lamps  are 
designed  for  the  same  current  flow,  and  there- 
fore soms  method  is  necessary  for  holding  the 
current  in  the  circuit  constant.  For  this  purpose 
a  transformer  has  been  especially  designed 
by  the  General  Electric  Company  which  changes 
the  nearly  constant  impressed  voltage  to  con- 
stant secondary  current.  This  transformer  has 
been  so  well  designed  that  it  holds  the  second- 
ary current  within  1/10  of  an  ampere  of  its  nor- 
mal value  from  no  load  to  full  load,  even  with  a 
5%  variation  in  impressed  voltage.  This  trans- 
former gives  a  closer  regulation ,  higher  efficiency 
and  a  better  power  factor  than  any  other  con- 
stant current  regulator,  and  at  the  same  time  by 
keeping  the  primary  and  secondary  Circuits  sepa- 
rate, protects  the  generating  equipment  from 
any  accidents  due  to  grounds  or  short  circuits 
on  the  distributing  lines. 

The  series  socket  and  cut-out  is  very  necessary 
for  the  successful  operation  of  a  series  system, 
and  is  designed  for  two  special  purposes;  first, 
to  short-circuit  the  lamp  automatically  when  the 
filament  fails,  and  second,  to  permit  the  removal 
of  the  lamp  from  a  live  circuit  without  inter- 
rupting the  service. 

For  general  purposes  all  streets  may  be  di- 
vided into  four  classes : 


1.  Principal  business  streets. 

2.  Important  cross  streets  and  boulevards. 

3.  Residence  streets. 

4.  Outlying  districts. 

In  every  one  of  the  above  divisions  the  Mazda 
lamp  can  be  used  so  as  to  economically  give  an 
abundance  of  light,  and  in  most  cases  at  a  cost 
less  than  that  for  any  other  type  of  illuminant. 
Where  a  high  intensity  of  light  is  desired,  units 
of  about  200  or  350  candle-power  should  be  used, 
but  in  the  majority  of  cases  a  smaller  size  lamp 
will  be  found  more  suitable.  With  the  smaller 
lamps,  spaced  more  frequently,  more  uniform 
illumination  is  obtained,  less  glare  is  experienced 
and  the  general  lighting  effect  is  much  better. 
If  we  have  a  certain  minimum  intensity  on  the 
street  and  desire  to  keep  this  value  constant, 
but  to  double  the  distance  between  lamps,  then 
we  find  that  the  new  light  unit  must  be  at  least 
four  times  as  powerful  as  the  old  ones;  con- 
versely, if  we  decrease  by  half  the  distance  be- 
tween lamps  and  keep  the  same  minimum  illumi- 
nation our  new  light  sources  need  be  only  one- 
fourth  as  powerful  as  the  original  lamps.  It  will 
therefore  be  seen  that  the  saving  in  energy  in- 
creases very  rapidly  as  we  decrease  the  size  of 
the  lamps  and  their  distance  apart,  while  at  the 
same  time  maintaining  the  same  minimum  in- 
tensity of  light.  Consequently  the  Series  Mazda 
lamps  are  the  most  economical  illuminant  for 
streets  where  a  uniform  low  intensity  of  light  is 
desired. 

Upon  the  principal  business  streets  the  illumr 
nation  should  be  of  a  character,  both  in  bright- 
ness and  general  appearance,  to  bring  credit  to 
the  city.  For  this  class  of  street  lighting  the 
Mazda  lamp,  whether  in  multiple  or  series,  has 
been  a  popular  illuminant.  The  best  results 
have  been  obtained  from  posts  placed  opposite 
one  another  on  each  side  of  the  street,  at  a  dis- 
tance apart  slightly  greater  than  the  width  of 
the  street.  Five  lamps  per  post  are  commonly 
used,  enclosed  in  a  diffusing  globe,  and  of  a  size 
to  give  approximately  10  watts  per  running  foot 
of  street.  It  is  also  the  practice  to  use  combina- 
tion trolley  lighting  poles,  where  an  agreement 
can  be  reached  between  the  trolley  and  lighting 
company.  In  other  towns  where  the  ornamental 
feature  is  not  desired,  350  C.  P.  Mazda  lamps 
should  be  used,  and  equipped  with  a  24"  Radial 
Wave  reflector.  These  lamps  should  be  placed 
from  20  to  25  feet  above  the  ground,  and  about 
100  feet  apart. 

Upon  the  important  cross  streets  and  boul- 
evards either  one-light  ornamental  standards 
can  be  used,  placed  at  the  sides  of  the  streets,  or 
lamps  suspended  from  brackets,  and  equipped 
with  Radial  Wave  reflectors.  In  each  case  the 
lamp  should  be  placed  at  the  side  of  the  street 
so  as  to  reduce  the  glare,  for  the  foliage  often 

52 


requires  a  low  suspension  of  the  lamp.  Where 
the  foliage  does  not  interfere  with  the  distribu- 
tion of  the  light  the  lamp  should  be  placed  from 
15  to  20  feet  above  the  ground.  The  lamps 
commonly  used  are  the  60  and  100  C.  P. 

Upon  the  residence  streets  the  lamp  is  usually 
suspended  at  the  side,  as  it  is  less  expensive  than 
the  center  suspension,  and  gives  sufficient  il- 
lumination over  all  the  street,  except  where 
same  is  unusually  wide.  The  most  common 
equipment  consists  of  either  40,  60  or  80  C.  P. 
lamps,  equipped  with  20"  Radial  Wave  reflect- 
ors, and  placed  from  15  to  18  feet  above  the 
ground. 

In  the  outlying  districts  the  character  of  the 
lighting  depends  on  the  amount  of  money  avail- 
able for  this  work.  The  32  and  40  C.  P.  lamps 
are  generally  used  and  placed  about  15  feet 
above  the  ground.  Staggered  placing  of  units 
is  seldom  advisable  in  street  lighting,  as  it  makes 
the  outline  of  the  road  less  distinct,  especially 
where  there  are  curves. 
Rating  of  Lamps 

Owing  to  recent  improvements  in  lamp  manu- 
facture it  is  now  possible  to  supply  series  lamps 
for  a  definite  amperage  rather  than  for  an  am- 
pere range,  as  has  been  the  practice  heretofore. 

This  improvement  has  been  long  striven  for, 
as  it  permits  the  central  stations  to  use  one 
current  value  on  their  series  lines  and  thus 
make  all  their  apparatus  interchangeable.  It  is 
to  the  advantage  of  the  central  stations,  there- 
fore, that  in  all  new  installations  they  adopt  a 
standard  ampere  value,  preferable  6.6,  and  also 
that  they  change  their  present  lines  to  the  near- 
est standard  current  value. 
The  standard  amperages  are  as  follows : 
Ampere  Range  of  Standard  Ampere 

Lamps  Used  in  Lamps  to  be  Used 

the  Past  in  Future 

3.0  to  3.8  3.5 
3.8  to  4.3  4.0 

5.1  to  5.9  5.5 
6.1  to  6.9  6.6 
7.0  to  8.0                                              7.5 

Mill  Lighting 

In  mill  work  the  quality  of  illumination  plays 
an  important  part  in  the  efficiency  of  production. 
In  a  well  lighted  mill  the  actual  operating  hours 
may  be  increased,  thereby  increasing  the  out- 
put, while  the  fixed  charges  remain  the  same- 
Spoilage  has  proven  to  be  the  chief  obstacle  to 
economical  production  in  mill  work.  Census 
experts  claim  that  25%  of  the  total  spoilage  can 
be  avoided  by  good  illumination.  The  employee, 
considered  as  a  unit  with  his  machine,  works  at 
least  2%  more  efficiently  under  good  than  under 

53 


poor  illumination.  Furthermore,  the  employee 
of  several  years'  service,  will,  by  virtue  of  his 
long  training,  be  highly  efficient,  provided  his 
eyesight  has  not  been  injured  by  working  under 
poor  illumination.  An  investment  in  a  good 
lighting  system  is  a  good  insurance  against  lia- 
bility for  accident.  This  is  borne  out  by  statis- 
tics, which  show  that  the  greatest  number  of 
industrial  accidents  occur  in  those  months  which 
average  the  greatest  number  of  hours  of  dark- 
ness and  gloom. 

The  effect  of  well  lighted  surroundings  upon 
the  employee  is  also  a  consideration  not  to  be 
neglected.  No  far  sighted  mill  man  would  cut 
off  his  heat  supply  during  the  winter  months  to 
reduce  his  operating  expense.  The  same  should 
be  said  about  his  illumination,  as  a  man  whose 
mill  is  well  illuminated  removes  by  several  de- 
grees the  likelihood  of  labor  disturbances. 

The  General  Electric  Company  has  a  complete 
line  of  information  covering  any  class  of  lighting 
service.  A  request  for  advice  on  any  phase  of 
lighting  service  will  secure  a  Bulletin  giving  a 
review  of  conditions  to  be  met  with,  and  recom- 
mendations for  securing  the  best  results.  Recom- 
mendations for  the  lighting  of  Textile  Mills  are 
given  below,  and  in  the  table  beginning  on  page 
23  will  be  found  the  intensities  recommended 
for  various  other  classes  of  lighting  service. 

Recommendations 


Cotton  Processes 

OPENERS. 

One    40   watt  Mazda  lamp  with    extensive 

Holophane  D'Olier  reflector  over  each  end 

of  machine. 
PICKERS. 

Same  as  Openers. 
CARDING. 

One  40  watt  Mazda  lamp  with  extensive  steel 

reflector,  per  machine  staggered. 
DRAWING  FRAME. 

One  40   watt  Mazda  lamp     with  extensive 

D'Olier  reflector,  spaced  8  feet. 
ROVING  FRAMES. 

Two  40  watt   Mazda  lamps   with    extensive 

reflectors  in  aisle,  spaced  7'  to  10'. 
RING  SPINNING. 

Two  60  watt  Mazda  lamps  with   extensive 

reflectors  in  aisle,  spaced  every  100  spindles 

on  each  side  of  alley. 
TWISTING. 

Same  as  Ring  Spinning. 

SPOOLERS. 

Two  60  watt  Mazda  lamps  with  extensive 
reflectors  in  aisle,  spaced  7'  to  10'. 

54 


WARPING. 

One  60  watt  Mazda  lamp  with  extensive  re- 
flector over  beam. 

One  60  watt  Mazda  lamp  with  intensive  re- 
flector over  or  inside  rack.  General  illumi- 
nants  when  warpers  are  movable. 

SLASHER. 

One  40  watt  Mazda  lamp  with  expensive  re- 
flector at  each  end  of  the  machine. 

DRAWING  IN. 

General  illumination  in  portion  of  mill  for 
drawing  in  furnished  by  40  watt  Mazda 
lamps,  with  extensive  reflectors,  spaced  10 
centers.  Supplemented  by  special  lights  on 
each  stand. 

WEAVING. 

Looms  for  light  colored  goods  up  to  42//,  one 
60  watt  Mazda  lamp  with  extensive  reflector, 
at  center  of  square  formed  by  four  machines. 
Looms  for  54-72  inch  goods,  one  60  watt  Maz- 
da lamp  with  extensive  reflector  at  each  end 
of  machine  in  weaver's  alley. 

INSPECTING. 

One  60  watt  Mazda  lamp  with  intensive  re- 
flector over  each  table. 

PACKING  AND  SHIPPING. 

General  illumination,  100  watt  Mazda  lamp 
with  extensive  reflector  hung  12  feet  above 
floor,  spaced  about  15  to  18  foot  centers. 

Silk  Processes 


WINDING  FRAMES  AND  THROWING  FRAMES. 
Three  60  watt  Mazda  lamps  with  extensive 
reflectors,  placed  in  aisle,  spaced  7'  to  10'. 

QUILLING. 

Two  60  watt  Mazda  lamps  with  extensive  re- 
flectors in  aisle,  spaced  5'  to  10'. 

WARPING. 

One  60  watt  Mazda  lamp  with  extensive  re- 
flector over  creel. 

One  60  watt  Mazda  lamp  with  intensive  re- 
flector over  reed. 

One  60  watt  Mazda  lamp  with  extensive  re- 
flector over  reel. 

WEAVING. 

One  60  watt  Mazda  lamp  with  intensive  re- 
flector over  lay  of  loom. 

One  40  watt  Mazda  lamp  with  extensive  re- 
flector in  rear  alley. 

FINISHING. 

One  60  watt  Mazda  lamp  with  intensive  re- 
flector over  each  table. 

PACKING  AND  SHIPPING. 

100  watt  Mazda  lamp  with  extensive  reflec- 
tor, 12  feet  high,  spaced  15''  to  18'. 

55 


Woolen  Processes 


PICKING  TABLE. 

One  40  watt  Mazda  lamp  with  intensive  re- 
flector over  each  table.  If  tables  are  placed 
back  to  back,  one  60  watt  Mazda  lamp  with 
extensive  reflector. 

WASHING. 

General  illumination,  100  watt  Mazda  lamps 
with  extensive  reflectors.  12'  above  floor, 
spaced  10'  to  12'. 

COMBING. 

General  illumination,  100  watt  Mazda  lamps 
with  extensive  reflectors,  10  to  12  feet  hig'h 
with  10  to  12  foot  centers. 

CARDING. 

One  40  watt  Mazda  lamp  with  extensive  re- 
flector per  machine  staggered. 

TWISTING. 

40  watt  Mazda  lamps  with  extensive  reflect- 
ors, 7'  above  floor  in  aisle,  7'  to  10'  centers. 

DYE  HOUSES. 

Illumination  can  be  greatly  improved  if  ven- 
tilating fans  are  used  to  draw  off  steam. 
Place  one  100  watt  Mazda  lamp  with  exten- 
sive reflector  between  every  other  tank. 
Raw  stock  dyeing  machine,  one  60  watt  Maz- 
da lamp  with  extensive  reflector  in  front  of 
each  machine. 

Skein  and  slubbing  dyeing  machines,  one 
60  watt  Mazda  lamp  with  extensive  reflector 
in  front  of  each  machine. 

DRAWING  IN. 

General  illumination  in  portion  of  mill  de- 
voted to  drawing,  in  60  watt  Mazda  lamps 
with  extensive  reflectors  spaced  S/  centers. 

WARPING. 

60  watt  Mazda  lamp  with  extensive  reflector 
over  reel.  60  watt  Mazda  lamp  with  inten- 
sive reflector  over  reed. 

WEAVING. 

One  60  watt  Mazda  lamp  with  intensive  re- 
flector over  lay  with  36"  goods. 
Two  40  watt  Mazda  lamps  with  intensive  re- 
flectors over  looms  weaving  54"  goods. 
One  40  watt  Mazda  lamp  with  extensive  re- 
flector in  rear  alley.     (If  black  cloth,  use  100 
watt  Mazda  lamp  for  36",  and  two  60  watt  for 
54"  goods) . 

PERCHING. 

One  100  watt  Mazda  lamp  with  intensive  re- 
flector over  each  perching  frame.  If  perch- 
ing frames  are  portable,  by  general  illumina- 
tion with  150  watt  Mazda  lamps  with  exten- 
sive reflectors,  !(/  to  12'  above  floor,  spaced 

56 


12'  to  15'  centers;  if  dark  cloth  is  perched,  250 
watt  Mazda  lamps,  15'  to  18'  centers. 
PACKING  AND  SHIPPING. 
Same  as  above. 

Knitting 

KNITTING— RIB,  TOP,  SHIRT  BODY,  AUTOMATIC 

SEAMLESS  AND  COLOR  STRIPER. 

Machines  generally  placed  in  groups,  one 
60  watt  Mazda  lamp  with  extensive  reflector 
to  every  four  machines. 

FLAT  KNITTERS. 

Place  60  watt  Mazda  lamps  with  extensive 
reflectors  in  aisle,  spaced  6'  to  8'  centers. 

LOOPING  AND  SEAMING  MACHINES.    FINISHING 

MACHINES. 

One  25  watt  Mazda  lamp  with  anchored  re- 
flector, hung  12"  above  table  and  18"  from 
head  of  machine. 

NAPPER  MACHINES. 

One  40  watt  Mazda  lamp  with  extensive  re- 
flector over  the  front  roll. 


General  Information  on   Incandescent 
Lamps 


History  of  the  Incandescent  Lamp 

The  first  commercial  incandescent  lamp  was 
introduced  by  Thomas  A.  Edison  in  1879.  The 
filament  was  horseshoe  shaped  and  was  made 
of  carbonized  paper.  The  essential  parts  of  the 
lamp  were  the  same  as  those  of  the  lamp  of  the 
present  day.  The  efficiency  at  which  the  lamp 
operated  was  about  7  watts  per  candle.  Later 
the  efficiency  was  increased  to  5.8  \vatts  per  can- 
dle by  the  adoption  of  a  carbonized  strip  of 
bamboo.  This  increased  the  total  life  of  the 
lamp,  yet  the  candle-power  declined  approxi- 
mately 20%  in  the  first  100  hours.  Further  im- 
provement in  1881  increased  the  efficiency  to  4.6 
watts  per  candle.  The  present  carbon  filament 
is  made  by  dissolving  absorbent  cotton,  forming 
a  thick  viscous  solution,  which  is  forced  under 
pressure  through  a  die,  forming  a  long  thread- 
like filament,  which  is  then  carbonized.  The 
efficiency  of  the  present  carbon  filament  is  ap- 
proximately 3.1  watts  per  candle. 

The  next  important  step  in  the  development 
of  the  incandescent  lamp  was  the  "metalliza- 
tion" of  the  Carbon  filament.  This  was  placed 
on  the  market  as  the  Gem  lamp  by  the  General 
Electric  Company.  The  Gem  filament  is  pro- 
duced, by  heating  the  ordinary  treated  Carbon 
filament  in  an  electric  furnace  to  a  very  high 
temperature.  The  cold  resistance  of  the  fila- 
ment is  considerably  reduced  by  this  heating, 
and  the  temperature  coefficient  is  changed  from 
negative  to  positive.  This  improvement  is  shown 
in  the  resistance  curves  on  page  73.  The  re- 
fractoriness of  the  filament  is  increased  suffi- 
ciently to  permit  its  operating  at  a  temperature 
some  200°  higher  than  the  carbon  filament  for 
the  same  deterioration.  The  most  important 
advantage  is  the  increase  in  efficiency,  the  Gem 
lamp  operating  at  2.5  watts  per  candle  as  com- 
pared -with  3.1  watts  per  candle  for  the  Carbon. 

The  Tantalum  lamp  was  placed  on  the  market 
in  1906.  It  had  an  added  efficiency  over  the 
Gem,  operating  at  2  watts  per  candle.  As  the 
Tantalum  lamp  gave  rather  unsatisfactory  ser- 
vice on  alternating  current  it  has  given  way  to 
the  more  efficient  Mazda  lamp.  The  metal  tung- 
sten of  the  Mazda,  filament  has  a  high  melting 
point,  and  high  vaporizing  temperature.  These 
qualities  are  essential  to  a  good  filament.  The 
tungsten  filament  is  also  a  poor  radiator  of  heat, 
and  accordingly  operates  more  efficiently  than 
the  Carbon  filament.  The  high  efficiency  of  the 

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Cost  per  1000 
Candle-hours 
of  light 

59 


Tungsten  filament  is  further  due  to  selective  ra- 
diation as  defined  on  page  2.  The  average  effi- 
ciency of  the  pressed  filament  Mazda  lamp  was 
about  1-23  watts  per  candle,  with  a  life  of  1000 
hours. 

Pure  tungsten  metal  has  a  very  bright  steel 
gray  appearance,  is  very  heavy,  having  a  spe- 
cific gravity  of  19  12,  and  until  recently  was  pro- 
duced only  in  a  brittle  form.  Recently  improved 
methods  of  manufacturing  tungsten  into  wire 
made  it  possible  to  produce  the  drawn  wire  Maz- 
da lamp.  The  possibility  of  producing  tungsten 
wire  in  great  lengths  has  permitted  a  change  in 
the  construction  of  the  lamp,  by  which  a  con- 
tinuous filament  is  employed,  instead  of  welding 
four  or  five  filament  loops  together,  as  was  done 
in  the  past.  This  new  construction  furnishes  a 
lamp  ihat  is  many  times  stronger  than  the 
pressed  filament.  This  lamp  operates  at  an  av- 
erage efficiency  of  1.15  watts  per  candle  with  a 
life  of  1000  hours. 

The  temperature  of  the  Mazda  filament 
reaches  about  2300°  Centigrade  when  operated  at 
1  watt  per  candle,  and  between  2100°  and  2200° 
Centigrade  when  operated  at  1.25  watts  per  can- 
dle. The  filament  has  a  high  positive  tempera- 
ture coefficient  so  that  a  remarkably  steady 
candle-power  is  obtained  over  a  comparatively 
wide  range  of  voltage.  This  is  shown  by  the 
curves  on  page  71.  Due  to  the  high  positive 
temperature  coefficient  the  current  density  re- 
mains fairly  constant  insuring  a  uniform  life. 


Etching  and  Frosting 

Etching 

The  process  of  etching  lamps  with  names, 
letters,  symbols,  etc.,  is  simple  and  inexpensive, 
out  when  done  by  the  manufacturer  will  cause 
delay  in  shipment,  as  it  specializes  every  order. 
The  following  instructions  will  enable  customers 
to  etch  their  own  lamps,  but  it  should  be  borne 
in  mind  that  the  solution  described  will  not  give 
satisfactory  results  for  frosting: 

Mix  in  a  small  lead  or  rubber  cup  a  good  grade 
of  hydrofluoric  acid,  and  crystalline  ammonium 
carbonate  until  the  acid  is  partly  neutralized. 
This  can  be  determined  by  a  test;  if  too  little  of 
the  carbonate  is  present,  the  etching  is  more 
of  a  transparent  eating  of  the  glass.  To  obtain 
clear  cut  letters  or  symbols,  spread  a  little  of  the 
acid  on  a  rubber  pad  with  a  tooth  brush,  or  some- 
thing similar,  then  spread  the  solution  on  the 
rubber  stamp  to  be  used,  taking  it  from  the  pad 
with  a  brush.  Ordinary  blotting  paper  may  be 
used  to  remove  an  excess  of  acid  from  the  stamp. 
Now  take  a  lamp  and  apply  the  rubber  stamp  to 
the  part  to  be  etched ;  this  part  of  the  lamp,  pre- 
vious to  applying  the  stamp,  should  be  heated 

60 


over  an  ordinary  gas  flame  to  a  temperature 
that  will  render  the  lamp  uncomfortable  to  the 
touch.  A  gas  heater  can  be  made  of  a  per- 
forated strip  of  sheet  iron,  arranged  so  that  a 
tray  of  about  50  lamps  can  be  placed  on  top  of  it 
with  the  base  or  tip  of  the  lamp  down,  so  as  to 
heat  the  part  to  be  etched.  Be  sure  to  return  the 
etched  lamps  to  the  tray  for  reheating,  as  this 
gives  better  and  quicker  results. 
Frosting 

The  term  "frosted"  lamp  is  used  to  describe 
a  lamp  with  a  frosted  or  etched  bulb.  Lamps 
may  be  permanently  frosted  by  either  sand- 
blasting or  acid  etching,  both  processes  giving 
results  so  similar  that  it  is  difficult  to  distinguish 
them.  The  acid  method  is  used  entirely  in 
the  frosting  of  Edison  lamps.  Although  the 
mixing  of  the  etching  paste  is  comparatively 
simple,  it  is  dangerous  to  handle  and  difficult  to 
secure  good  results.  For  this  reason  it  is  not 
advisable  for  customers  to  do  their  own  frosting. 

The  regular  acid  frosting  is  applied  to  Carbon, 
Gem  and  Miniature  lamps  of  all  classes.  The 
"satin  finish"  frosting  is  used  on  regular  mul- 
tiple Mazda  lamps.  This  is  a  more  expensive 
operation,  and  is  known  as  the  German  process. 
The  solution  is  more  or  less  a  paste.  Lamps  are 
dipped  in  the  paste,  allowed  to  stand  for  some- 
time, and  are  then  rinsed  in  water.  The  finish 
is  smooth  and  satin  like. 

The  principal  styles  of  frosting  are  "bowl" 
frosting,  "full"  frosting  and  "bulls  eye"  frosting. 
In  full  frosting  the  entire  bulb  is  frosted.  In  bowl 
frosting  only  the  lower  part  or  the  bowl  of  the 
bulb  is  frosted.  In  bulls  eye  frosting  the  whole 
bulb  is  frosted,  excepting  a  clear  spot  2  inches  in 
diameter.  This  type  of  frosting  is  sometimes 
used  for  stereopticon  lamps. 
Colored  Lamps 

Colored  lamps  can  be  supplied  with  bulbs  made 
of  either  clear  glass  superficially  colored  or  of 
natural  colored  glass.  Superficially  colored  bulbs 
are  bulbs  which  have  had  a  dipping  or  coating  of 
color  applied  to  their  exterior  surfaces ;  their 
color  is  not  weather  proof.  Natural  colored 
bulbs  are  bulbs  made  from  permanently  colored 
glass  ;  their  color  is  weather  proof. 


The  Best  Lamp 

The  fallacy  of  the  contention  that  the  lowest 
price  lamp  is  the  best  lamp  lies  in  the  assumption 
that  a  lamp's  value  is  measured  solely  by  its 
first  cost,  instead  of  by  its  ultimate  cost.  The 
first  cost  or  price  of  a  lamp  is  but  a  fraction  of 
its  ultimate  or  true  cost,  and  completely  ignores 
useful  life,  efficiency  and  cost  of  power,  which 
are  the  most  important  factors  of  a  lamp's  cost. 

61 


To  illustrate  what  a  small  percentage  the  first 
cost  is  of  the  ultimate  cost  and  to  set  forth  its 
incorrectness  as  a  standard  of  lamp  value  let  us 
assume  that  a  carbon  50.0  watt,  2.97  w.p.c.  lamp 
has  a  useful  life  of  700  hours,  that  its  price  is  16c, 
and  that  power  costs  5c  per  kilowatt-hour: 

Then     50  x  70°     -  35.00  kilowatt-hours. 
1000 

35.00  X  .05  =  $1.75  or  cost  of  power 

Price  of  lamp  =  .16 

Therefore  $1.91  equals  ultimate  cost  of  lamp 

But Price  of  lamp _.  ^16_  =  Qi084 

Ultimate  cost  of  lamp        1.91 
or  8.4  per  cent. 

Therefore  while  the  first  cost  of  the  lamp  at 
this  life  and  efficiency  is  but  8.4  per  cent,  of  its 
ultimate  cost,  the  cost  of  power  is  91  per  cent, 
of  its  ultimate  cost  or  nearly  11  times  the  price 
of  the  lamp. 

Is  the  best  lamp  the  lamp  that  lasts  the  longest 
or  gives  the  longest  actual  life? 
Let  us  consider: 

The  actual  life  of  a  lamp  fails  not  only  to  com- 
prise the  important  factors  in  lamp  service  of 
useful  life,  efficiency  and  cost  of  power,  but 
ignores  also  the  price  of  the  lamp.  Therefore, 
the  actual  life  can  be  no  criterion  of  a  lamp's 
quality.  Besides,  experience  demonstrates  that 
long  actual  life  is  usually  attained  only  at  the 
expense  of  candle-power  and  efficiency.  Lamps 
are  made  for  the  twofold  purpose  of  giving  light 
and  life,  not  mere  life  alone,  but  useful  life — life 
with  candle  power. 

We  therefore  conclude  that  the  best  lamp  is 
not  the  lamp  that  sells  at  the  lowest  price  nor 
the  lamp  that  lasts  the  longest,  but  is  the  lamp 
whose  ultimate  cost  is  the  lowest,  i.e.,  the  cost 
of  the  lamp  and  the  cost  of  power:  or  with 
equal  price  and  economy  the  lamp  that  gives  the 
longest  useful  life. 

It  is  a  fact  demonstrated  by  test  and  practical 
experience  that  the  Edison  Gem  and  Mazda 
lamps  surpass  any  and  all  makes  in  these  desir- 
able qualities.  Compared  with  the  products  of 
other  manufacturers  they  are,  therefore,  the 
cheapest  lamps  to  use,  although  the  prices  are 
not  always  the  lowest.  That  they  alone  are  en- 
titled to  the  distinction  of  "best"  is  shown  by  the 
claims  made  for  other  lamps  that  they  are  "as 
good  as  the  'Edison,'  etc." 

Characteristics  of  the  Best  Lamp 
The  best  lamp  has  the  following  distinguish- 
ing features: 

a— Absence  of  physical  defects. 

b— Correctness  of  rating. 

c — Uniformity  of  performance. 

62 


d— Maintenance  of  candle-power. 
e— Low  ultimate  cost  of  operation. 

Edison  lamps  are  carefully  inspected  after 
each  step  in  their  manufacture  and  are  then 
subjected  to  a  rigid  final  inspection  before  being 
sent  out. 

The  lamps  are  carefully  tested  and  selected  to 
give  the  proper  ratings. 

It  is  not  sufficient,  however,  that  lamps  ini- 
tially meet  all  requirements;  they  must  also, 
after  installation,  give  uniform  useful  life,  and 
during  that  life  afford  uniform  candle-power  and 
consume  uniform  watts  or  power;  thereby  ren- 
dering that  uniform  and  definite  lamp  service 
which  is  so  essential  to  good  lighting.  Uniform 
useful  life  makes  possible  the  adoption  of  a  sim- 
ple and  effective  system  of  lamp  renewals  and 
also  serves  as  an  excellent  index  of  the  efficiency 
at  which  the  lamps  are  operated.  Uniform 
candle-power  precludes  unsatisfactory  light  con- 
trasts and  insures  even  illumination.  Uniform- 
watt  or  power  consumption  prevents  complaints 
of  excessive  and  uncertain  meter  bills:  it  elimi- 
nates the  question  of  allowance  to  customers 
which  is  an  undesirable  source  of  friction  and 
is  the  result  of  unsatisfactory  and  expensive 
lamp  service;  and  it  also  insures  stations  which 
sell  light  by  contract  against  loss  due  to  excessive 
wattage  or  power  consumption  for  which  there  is 
no  pecuniary  return. 

An  ideal  lamp  would  be  one  that  maintained 
its  initial  candle-power  throughout  its  life.  So 
then,  other  conditions  being  equal,  the  best  lamp 
is  the  lamp  that  at  a  definite  w.p.c.  maintains  its 
candle-power  for  the  longest  time,  or  the  lamp 
that  gives  the  best  useful  life. 

In  conclusion,  it  pays  most  decidedly  to  use 
carefully  selected  lamps,  because  the  saving  to 
the  lamp  user  is  worth  many  times  the  saving  in 
first  cost  of  a  few  cents  which  the  care- 
less and  incompetent  lamp  manufacturer  offers 
as  an  inducement  to  use  his  lamps.  The  amount 
paid  for  the  extra  wattage  consumption  of  an 
inefficient  lamp  during  its  useful  life  is  often  six 
or  seven  times  the  first  cost  saving.  It  costs  the 
careful  and  competent  manufacturer  much 
money  to  inspect  his  product  rigidly  and  hon- 
estly, to  test  and  select  his  lamps  carefully,  and 
to  weed  and  cull  out  the  imperfect  ones.  The 
user  has  the  choice  of  wisely  paying  the  full 
price  for  reliable  results  or  of  buying  on  price 
only,  and  of  paying  far  more  finally  through 
failure,  breakage  and  increased  consumption  of 
power. 


Cleaning  Mazda  Lamps. 

Where  no  regular  provision  is  made  for  clean- 


63 


ing  lamps,  it  is  safe  to  say  that  the  lighting  would 
be  increased  15%  by  the  introduction  of  such 
service.  With  monthly  cleaning  the  average 
loss  of  light  due  to  dust  will  in  most  cases  be  only 
2  or  3%.  For  a  100  watt  unit  burning  1000  hours, 
per  year  with  energy  at  10  cts.  per  kw-hr.  the 
total  operating  cost  will  be  about  $12.00  and  15% 
of  this  is  $1.80.  The  cost  of  cleaning  this  lamp 
monthly  will  amount  to  from  25  to  35  cts.  per 
year,  which  means  a  saving  in  light  of  $1.45  to 
$1.55  perlamp  per  year  by  keeping  the  lamp  clean. 

Consider  the  case  of  a  250  watt  Mazda  lamp  in 
an  industrial  plant  where  the  units  are  used  4000 
hrs.  per  year  and  energy  costs  2  cts.  per  kw-hr. 
The  total  cost  of  operation  is  approximately  $26 
and  a  15%  saving  amounts  to  $4.00.  The  units 
can  be  cleaned  once  a  month  for  about  40  cts.  per 
year,  which  is  a  saving  in  light  of  $3.60  per  lamp 
per  year. 

These  figures  apply  to  average  installations  but 
in  many  instances  the  saving  would  be  greater. 

There  are  any  number  of  schemes  for  cleaning 
lamps  and  reflectors.  In  offices,  stores  and  places 
of  such  character,  where  glass  reflectors  are  used, 
it  will  be  found  necessary  to  take  the  reflectors 
down  for  a  thorough  cleaning  only  once  every 
three  or  four  months,  and  when  the  lamps  are  re- 
newed. A  wet  cloth  used  with  a  bristle  brush  is 
sufficient  for  a  good  cleaning  until  reflectors  are 
taken  down  for  washing.  In  cleaning  lamps  dry 
woolen  or  silk  cloths  should  never  be  used,  as  the 
static  electricity  developed  may  cause  the  fila- 
ment to  break.  Always  use  a  cotton  cloth  or 
cotton  waste.  In  textile  mills  and  places  where 
only  a  coating  of  dust  settles  on  the  lamps  and 
reflectors  a  dry  cloth  is  all  that  is  necessary  to 
put  the  lamps  in  good  condition.  In  mills  and 
shops  where  steel  and  enamel  reflectors  are  used 
and  where  more  or  less  grease  accumulates  on 
the  reflector,  a  bunch  of  cotton  waste  and  some 
gasolene  is  necessary  to  remove  the  dirt.  In  all 
case^,  it  is  seldom  necessary  to  remove  the  re- 
flectors in  order  to  clean  them. 

In  cleaning  Mazda  lamps  it  is  always  best  to 
have  the  lamp  burning.  Although  the  present 
drawn  wire  Mazda  lamp  is  very  much  stronger 
than  its  predecessor,  the  pressed  filament  lamp, 
this  minor  precaution  of  switching  on  the  cur- 
rent for  one  or  two  minutes  will  often  prevent 
broken  lamps. 

Drawn  Wire  Mazda  Lamps 

The  drawn  wire  filament  of  the  present  Mazda 
lamp  is  many  times  stronger  than  the  old  pressed 
filament  at  any  time  during  its  life.  This  fila- 
ment is  continuous  and  of  uniform  size,  so  that 
uneven  heating  of  any  part  of  the  filament  is 

64 


impossible.    This  quality  has  much  to  do. with 
the  uniform  life  of  this  lamp. 

The  essential  qualities  of  an  incandescent  fila- 
ment are:— 

1.  High  Melting  point 

2.  Low  vapor  tension 

3.  Proper  radiating  characteristics 

4.  High  resistance. 

The  higher  the  temperature  at  which  a  given 
incandescent  filament  operates  the  greater  the 
quantity  of  light  radiated  in  proportion  to  the 
energy  used.  The  increase  of  light  emitted  is 
very  marked  at  high  temperatures,  so  that  a 
slight  increase  of  temperature  of  an  incan- 
descent filament  means  a  large  increase  in  the 
amount  of  light  given  off.  The  melting  point  of 
Tungsten  is  higher  than  those  of  other  materials 
now  used  for  filaments. 

Low  vapor  tension  is  very  important,  as  it  is 
necessary  that  the  filament  does  not  evaporate 
rapidly  at  high  temperatures.  The  drawn  wire 
filament  is  especially  ideal  in  this  particular  as 
tungsten  has  a  low  vapor  tension. 

The  drawn  wire  tungsten  filament  is  a  poor 
radiator  of  heat,  so  that  at  the  same  temperature 
it  will  emit  more  light  than  a  carbon  filament, 
The  superior  light  giving  quality  of  the  Mazda 
filament  is  due  in  part  to  the  fact  that  a  rela- 
tively large  per  cent,  of  the  energy  radiated  falls 
within  the  limits  of  the  visible  spectrum, 

High  specific  resistance  is  a  desirable  feature 
of  an  incandescent  filament  in  that  it  allows  the 
use  of  a  thick  and  short  filament.  The  positive 
temperature  coefficient  of  the  Mazda  filament  is 
another  valuable  feature,  as  it  insures  a  more 
nearly  uniform  candle-power  on  fluctuating  volt- 
age. The  effect  of  this  positive  temperature 
coefficient  is  shown  in  the  curves  on  page  71. 

Types  of  Mazda  Lamps 

Mazda  lamps  of  the  regular  type  are  made  in 
sizes  of  10, 15, 20, 25, 40,  60, 100, 150  and  250  watts,  for 
voltage  ranges  of  100  to  130,  and  200  to  260, 
excepting  the  15  and  20  watt  lamps,  which  are 
made  for  100  to  130  volts  only.  These  are  fur- 
nished in  straight  side  bulbs  designated  by  the 
letter  "S,"  and  the  extreme  diameter  in  eighths 
of  an  inch,  as  for  example:  the  S-17  bulb  has  a 
diameter  of  2-1/8  inches.  The  round  bulb  types 
are  made  in  sizes  of  15,  25,  40,  60,  100,  150,  400  and 
500  watts  for  the  100  tc  130  volt  range,  and  in  sizes 
of  25,  40,  60,  100  and  500  watts  for  the  200  to  260 
volt  range^  The  round  bulbs  are  designated  by 
the  letter  "G."  A  tubular  lamp  is  made  in  the 
25  watt  size  for  the  100  to  130  volt  range.  This 
bulb  is  designated  by  the  letter  "T." 

A  concentrated  filament  lamp  is  made  in  the 
100  watt  size,  round  bulb,  for  the  same  voltage 
range. 

65 


The  schedule  of  Mazda  Sign  lamps  is  shown 
complete  on  page  42. 

Large  style  lamps  for  20  volts,  and  below,  are 
made  as  follows: — 

2.5,  5,  7.5  and  10  watts  in  the  S-14  bulb, 

10,  12.5  and  15  watts  in  the  S-17  bulb. 

15,  20,  25  and  30  watts  in  the  S-19  bulb. 

2.5,  5,  7.5,  10,  12.5,  15,  20,  25  and  30  watts  in  the 
G-16K  bulb. 

Mazda  St.  Series  lamps  are  made  for  the  fol- 
lowing ampere  ranges,  and  in  the  following 
candle-power  sizes:  3.  to  3.8  amperes  in  32,  40, 
60  and  80  C.P.  sizes;  3.8  to  4.3  amperes  in  32,  40, 
60,  80,  100,  200  and  350  C.P.  sizes;  5.1  to  5.9  am- 
peres in  32,  40,  60,  80,  100,  200  and  350  C.P.  sizes : 
6.1  to  6.9  amperes  in  32,  40,  60,  80,  100,  200  and  350 
C.P.  sizes;  7.  to  8.  amperes  in  32,  40,  60,  80  and 350 
C.P.  sizes. 

Train  lighting  lamps. — The  Gem  berth  lights 
are  made  in  sizes  of  15  and  20  watts  in  the  G-12 
bulb.  The  Mazda  Train  Lighting  and  Compen- 
sator lamps  are  made  as  follows:  25  to  34  volts 
and  50  to  65  volts  in  sizes,  10,  15,  20,  25  and  50 
watts  in  the  round  bulbs,  and  in  sizes,  10,  15,  20, 
25,  40  and  50  watts  in  the  "S"  bulbs. 

Mazda  Street  Railway  Lamps  are  made  in  23 
and  36  watt  sizes.  100  to  130  volts,  to  operate  five 
in  series  on  circuits  of  500  to  650  volts,  and  are 
especially  selected  for  amperes.  In  addition  to 
the  standard  Mazda  Railway  Lamps,  Mazda 
Gauge  Lamps  of  10  volts  are  supplied  for  use  in 
series  with  the  standard  lamps. 

Automobile  and  Electric  Vehicle  lamps  are 
given  on  page  36. 

Gem  Lamps 

The  Edison  Gem  or  metallized  filament  lamp, 
although  not  as  efficient  as  the  Edison  Mazda 
lamp,  has  a  decided  advantage  over  the  Carbon 
lamp  as  a  low  initial  cost  unit. 

A  great  many  Central  Stations  give  free  re- 
newals on  Gem  lamps,  and  are  substituting  them 
\vatt  for  watt  for  Carbons.  The  substitution 
watt  for  watt  does  not  reduce  the  Central  station 
load,  but  gives  the  customer  a  20%  increase  in 
illumination  for  the  same  cost.  The  Gem  lamp 
gives  a  whiter  and  more  agreeable  light  and  due 
to  the  positive  temperature  coefficient,  is  steadier 
on  varying  voltages. 

In  private  plants  running  at  full  capacity,  the 
adoption  of  Gem  lamps  will  give  an  increase  of 
illumination  of  20%,  or  if  additional  space  is  to 
be  illuminated,  20%  of  the  generator  capacity 
may  be  secured  for  this  purpose  by  their  substi- 
tution. In  designing  a  new  private  plant  the 


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use  of  Gem  lamps  will  reduce  the  generator 
capacity,  thereby  cutting  down  the  first  cost  of 
boilers,  generators,  and  accessories  and  lower- 
ing the  fixed  charges  in  proportion.  The  de- 
crease of  wattage  for  private  plants  using  Gem 
lamps  in  preference  to  Carbons  is  shown  in  Ta- 
ble 18.  In  Table  19  is  shown  the  total  cost  for 
the  operation  of  Gem  lamps  for  1000  hours  ser- 
vi'ce. 

The  curves  in  Fig.  22  show  the  changes  in  the 
total  hours  life  of  the  Gem  and  Carbon  lamps 
for  varying  efficiences.  The  Gem  lamp,  as  will 
be  seen  from  this  curve,  will  burn  three  times 
as  long  as  a  Carbcn  lamp  operating  at  the  same 
efficiency.  For  a  given  hour's  life  the  Gem  lamp 
operates  17%  more  efficiently  than  the  carbon 
lamp. 


3300 

jr 

41 

3600  -- 

::  it:::     ::::: 

3400            Ge:n  F»lauient        j 

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2800                      -j  

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2000 

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1200                         r              -y 

1000                  J-           i 

800                /           / 

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200  ^--.^-  

1 

2.0      2.4      2.8     3.2      3.G      4.0      4.4      4.8 
Lamp  Efficiency  in  Watts  per  Candle 

Fig.  22 


69 


Average  Performance  of  Incandes- 
cent Lamps 

The  curves  shown  in  Fig.  23  represent  the 
average  performance  of  the  60  watt  Mazda,  the 
50  watt  Gem,  the  50  watt  Carbon  and  the  40  watt 
Tantalum  lamps,  which  have  been  tested  in  the 
laboratories  of  the  General  Electric  Company, 
Harrison,  N.  J.  These  curves  are  obtained  from 
lamps  operating  at  the  following  efficiencies:— 
Mazda  at  1.16  w. p. c.,  Gem  at  2.5  w.p.c.,  Carbon 
at  2.97  w.p.c.  and  Tantalum  at  1.79  w.p.c. 

During  the  first  100  hours  burning  the  candle- 
power  of  the  60  watt  Mazda  lamp  increases  1% 
and  decreases  beyond  that  point.  The  average 
candle-power  during  the  rated  commercial  life 
of  1000  hours  is  about  94%  of  the  initial  candle- 
power.  After  the  first  100  hours  the  specific  con- 
sumption increases  to  the  rated  life  or'  the  lamp, 
at  which  point  it  is  113.5%  of  the  initial  consump- 
tion, an  increase  of  .15  w.p.c. 

The  candle-power  of  the  Gem  lamp  increases 
2%  during  the  first  50  hours  burning,  then  de- 
creases through  the  rated  life  of  700  hours.  The 
average  candle-power  during  this  life  is  90%  of 
the  initial.  The  specific  consumption  decreases 
during  the  first  50  hours  and  then  increases  to 
117%  of  the  initial  at  the  end  of  700  hours,  an  in- 
crease of  .42  w.p.c. 

The  candle-power  of  the  50  watt  carbon  lamp 
increases  3%  during  the  650  hours  burning,  after 
reaching  this  point  it  falls  off  in  a  straight  line. 
The  average  candle-power  during  the  700  hours 
life  is  87.75%  of  the  initial  candle-power.  The 
specific  consumption  decreases  1.5%  at  the  end 
of  the  50  hours  burning,  then  increases  25%,  or 
.74  w.p.c.  at  the  end  of  700  hours. 

The  candle-power  of  the  40  watt  Tantalum 
lamp  increases  to  105%  during  the  first  70  hours 
burning.  There  is  a  steady  decline  beyond  this 
point  throughout  the  rated  commercial  life  of 
800  hours.  The  average  candle-power  for  the 
rated  life  is  90%  of  the  initial.  The  specific  con- 
sumption decreases  11%  during  the  first  70  hours, 
then  increases  in  a  straight  Une  to  119%  at  SCO 
hours,  an  increase  of  .35  w.p.c. 

The  lamps  upon  which  these  tests  were  made 
were  burned  tip  downward  and  with  the  excep- 
tion of  the  Tantalum  lamp  were  operated  on 
alternating  current.  These  results  may  be  con- 
sidered as  representative  of  all  sizes  of  the  types 
which  the  above  lamps  represent,  as  each  of 
these  lamps  closely  approximate  the  average  of 
their  respective  types.  Especially  is  this  true  of 
the  Mazda  and  G~em  lamps  for,  due  to  the  uni- 
formity of  the  method  observed  in  their  manu- 
facture, the  lamps  themselves  give  a  very  uniform 
performance,  individual  lamps  varying  very 

70 


200  400   COO  hCO  1000  1200  1400 

Life  iu  Hours 

Fig.  23 


I    Mazda 
--  Tantal 
_    _  _               Gem— 
190  -S-----  Carboi 

I88::::^i:?::: 
ITO::  :::Nss:5::: 

Um—  |         "150 

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o  130  -  Watts  per  :x*^    - 
^120-     Caudle  f"^r  - 

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U5     101)    105    110    1-13    120 
Percent  Volts 

Fig.  24 
71 


little  from  the  average  results  obtained  by  test. 
The  contrast  in  performance  as  shown  by  the 
curves  is  apparent  at  a  glance.  The  decline  of 
candle-power  and  the  increase  in  specific  con- 
sumption are  least  for  the  Mazda  lamps.  Thro- 
ughout its  life  this  lamp  has  very  nearly  a  uni- 
form performance,  the  slope  of  its  curves  being 
much  less  than  that  of  any  other  lamp. 

Characteristics  of  Lamp  Filaments 

In  Fig.  25  are  given  curves  showing  the  per- 
centage change  in  volts,  amperes,  watts,  and 
watts  per  candle,  accompanying  the  changes  in 
candle-power  of  Mazda  lamps.  Fig.  26  shows 
the  variation  in  resistance,  due  to  temperature 
changes,  of  the  Tungsten,  Tantalum,  Carbon, 
and  Gem  filaments  in  percentages  of  their  re- 


Percent  Wat 

00     000     §   2 

300   ,         --,-0005  — 
2vjQ|j  [I  1  1  |l||  1  ||  1  ||  HI  || 

280  tH 

270  —  • 

ts  per  Candle 

^SSSS^SiSSS 

25o|  !  1  1  1  1  1  !  HI  tlrn  nttt 

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-Percent  Volts,  Amperes  and  Watts 
Fig.  25 

72 


spective  cold  resistances.  As  can  be  seen  the 
Carbon  lamp  has  a  negative  temperature  coeffi- 
cient so  that  an  increased  voltage  means  a  de- 
crease in  resistance,  thereby  increasing  the 
variation  to  a  further  extent.  The  Tungsten 
filament,  however,  has  a  positive  temperature 
coefficient,  and  as  an  increase  of  voltage  means 
a  marked  increase  of  resistance  the  Change  of 
current  is  small  in  proportion  to  the  rise  of  volt- 
age. Due  to  this  positive  temperature  coeffi- 
cient the  Mazda  lamp  undergoes  smaller  changes 
in  candle  power,  efficiency  and  life  than  does 
the  carbon  filament. 

The  variations  of  candle-power  and  efficiency 
with  variations  of  voltage  are  shown  by  the 
curves  in  Fig.  24.  As  explained  above  these 
curves  show  that  the  Tungsten  filament  under- 
goes but  small  change  as  compared  to  the  other 
types  of  filaments. 


1400 


10      30      50     70     90     110 i  130 
20      40     60     80    100    120   140 
For  cent  oZ  Volts 

Fig.  26 


73 


Cost  of  Light 

The  average  total  cost  per  unit  of  light  pro 
duced  by  incandescent  lamps  may  be  considered 
as  made  up  of  two  elemental  parts,— cost  of 
energy  and  the  cost  of  renewals.  It  is  evident, 
then,  that  the  most  economical  efficiency  at  which 
a  lamp  can  be  operated  is  that  at  which  the  sum 
of  these  expenditures  is  lowest.  As  the  cost  of 
energy  becomes  higher,  or  as  the  cost  of  re- 
newals becomes  lower,  the  efficiency  should  be 
increased.  This  is  shown  by  the  curves  in  Figure 
28.  These  curves  show  the  economical  efficiencies 
at  which  a  250  watt  Mazda  lamp  should  operate 
for  various  charges  per  kilowatt  hour  of  energy. 

The  average  total  cost  in  dollars  of  1000  candle 
hours  of  light  is  equal  to 

Cost  per  kw-hr.  in  dollars  X  initial  efficiency 
factor 

, cost  of  lamp  in  dollars  X  1000 

hours  life  X  initial  candle-power  X  factor. 

The  factor  referred  to  in  the  above  formula  is 
the  -ratio  of  the  average  to  the  initial  candle- 
power  and  life.  These  values  are  : — 

Mazda .95 

Gem .85 

Carbon .80 

The  total  cost  of  a  number  of  hours  service  is 
composed  of  the  cost  of  energy  and  the  cost  of 
renewals  for  that  number  of  hours  as  shown  in 
the  formula  on  page  5.  Table  21  shows  the  total 
cost  of  lighting  for  1000  hours  service,  with 
the  various  sizes  of  Mazda  lamps,  Owing  to  the 
greater  efficiency  of  operation  there  is  a  great 
saving  effected  by  the  substitution  of  Mazda 
lamps  for  either  Carbon  or  Gem  lamps.  This 
saving  has  been  calculated  for  several  substitu- 
tions, and  the  results  are  given  in  Table  20.  As 
can  be  seen  in  this  table  the  Mazda  installation 
will  in  each  case  give  equal  or  higher  candle- 
power  than  the  replaced  Carbon  or  Gem  lamps. 

The  tables  referred  to  above  show  the  Mazda 
lamp  to  be  the  most  economical  lamp.  It  should 
be  remembered,  however,  that  in  general  this 
lamp  should  be  operated  at  high  operating  effi- 
ciency. Quite  often  in  installing  a  lighting  sys- 
tem a  lamp  is  specified  as  operating  at  high 
efficiency  for  a  voltage  two  volts  higher  than  the 
actual  voltage  at  the  lamps.  For  example,  a 
lamp  specified  as  operating  at  high  efficiency  at 
118  volts  will  operate  at  medium  efficiency  if  the 
actual  voltage  at  the  lamps  proves,  by  test,  to 
be  116  volts.  This  means  that  the  economy  of 
the  installation  is  decreased,  and  it  is  essential 
that  the  user  of  incandescent  lamps  makes  sure 
that  his  lamps  are  operating  at  the  proper  effi- 
ciency. Too  often  a  lamp  that  has  outlived  its 

74 


rated  life  is  allowed  to  remain  in  the  circuit- 
This  not  only  mars  the  appearance  of  the  instal- 
lation but  also  cuts  down  the  efficiency.  The 
wattage  consumption  remains  practically  the 
same,  so  that  the  user  of  a  lamp  that  has  passed 
its  rated  life  by  several  hours,  is  paying  for 
energy  that  does  not  produce  the  amount  of 
light  that  could  be  gained  by  renewal. 


0.2    0.4  0.6  0.8    1.0    1.2   1.4  1.6   1.8    2.0 

Rate  per  K\v.-hr.  in  Cents 

Fig.  27 

Curves  showing  total  cost  of  1000  candle-hours 
of  light  produced  by  various  types  of  lamps. 


75 


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79 


Energy  Losses  in  Incandescent 
Lamp  Filaments. 

Transmission  of  electrical  to  thermal  power  in 
incandescent  lamps  is,  so  far  as  known,  perfect 
and  without  loss.  The  heat  produced  in  the  fila- 
ment must,  in  the  steady  state,  escape  at  the 
same  rate  at  which  it  is  generated.  The  escape, 
or  heat  dissipation,  from  the  filament  must  occur 
by  radiation,  conduction,  or  convection.  Radi- 
ation is  believed  to  be  an  electro-magnetic 
process  whereby  electro-magnetic  waves  are 
set  up  in  the  space  surrounding  the  filament, 
and  are  transmitted  outwardly  in  all  directions 
at  the  velocity  of  light.  All  the  light  usefully 
delivered  by  the  lamp  is  due  to  this  radiation, 
and  depends  upon  how  much  radiation  is  pro- 
duced within  the  limits  of  the  visible  spectrum. 
The  major  part  of  the  radiation  given  off  by  the 
filament  is  non-luminous,  that  is,  it  has  a  fre- 
quency either  too  low  or  100  high  to  be  perceived 
by  the  eye.  Moreover,  some  of  the  radiation  in 
passing  through  the  glass  walls  of  the  lamp  is 
absorbed  and  heats  the  glass,  so  that  this  lost 
radiation  is  given  off  finally  by  air  convection 
from  the  bulb.  A  percentage  of  the  heat  escapes 
from  the  filament  by  conduction  through  the 
leads  and  through  the  supporting  anchors.  A 
part  of  the  heat  escapes  from  the  filament  into 
the  surounding  gas  by  convection.  This  is  neces- 
sarily only  a  small  part,  however,  and  depends 
upon  the  condition  of  the  vacuum. 

The  ratio  of  total  energy  radiated  to  the  power 
consumed  is  spoken  of  as  the  relative  radiation 
capacity.  >  The  ratio  of  luminous  radiation  to  the 
total  radiation  is  called  the  light  effect  and  the 
ratio  of  luminous  power  to  the  total  power  con- 
sumed is  the  useful  effect  or  net  efficiency.  The 
determination  of  these  relations  is  difficult  and 
various  schemes  have  been  used  for  their  meas- 
urement. The  values  given  in  the  table  are 
conclusions  arrived  at  by  different  experiments, 
and  an  average  of  the  values  for  each  relation  may 
be  considered  as  a  fair  approximation. 

In  the  pressed  filament  type  of  lamp  it  was 
necessary  that  the  filpment  have  good  electrical 
contact  with  the  bottom  anchors,  and  a  good 
electrical  contact  is  a  good  thermal  contact.  In 
the  drawn  wire  type  the  only  electrical  contacts 
are  at  the  lead  wires,  consequently  the  heat  loss 
due  to  conduction  is  less.  This  means  an  in- 
creased ratio  of  total  radiated  energy  to  total 
power  consumed.  A  comparatively  large  per- 
centage'of  the  radiation  from  the  drawn  wire 
filament  is  within  the  visible  spectrum,  so  that 
this  lamp  has  a  high  ratio  of  luminous  radiation 
to  total  radiation.  As  both  of  these  ratios  are 
high,  the  lamp  has  a  high  net  efficiency. 


•g 

£e£ 

id 

cj 

>> 

S'S 

ll'| 

H 

0 

fi 

J3  j 

-s|S 

h-3td 

0) 

s^ 

03 

«(SU 

^ 

< 

Carbon 

61.9 

2.85 

1.75 

3.8 

a 

1.56 

3.1 

115  Volt 

2.2 

2.85 

c 

3.1 

2.64 

250  Volt 

12.42-3.42 

3.1 

b 

Tantalum 

64.8 

4.26 
6.35-6.66 

2.75 

2.02 
1.97 

a 
b 

Osram                  '     75.6         4.63 

3.5 

151 

a 

Tungsten 

250  Volt 

7.6-9.39 

1.31 

b 

130  Volt 

6.43-6.61 

I   1.28 

b 

4.5 

1.31 

115  Volt 

5.2 

1.18 

c 

6.00 

1.05 

References : 

Electrical  World,  March  9,  1911,  Page  593. 
a-     Elek.  Zeit.,    March    16,    1911,  G.    Leimbach, 

E.  World,  April  27,  1911. 

b-    Electrical  World,  May  18, 1911 ,  R.  A.  Houston, 
c-    Elek.  Zeit.,  Oct.  12,  1911,  J.  Russner, 

Electrical  World,  April  20,  1911,  Page  982. 

Prevention  of  Static  Effects 

Incandescent  lamp  filaments  are  sometimes 
affected  by  static  electricity  from  moving  belts, 
silk,  etc.  As  a  means  of  preventing  any  trouble 
from  this  source  a  metallic  comb  consisting  of  a 
row  of  sharp  projecting  teeth  is  placed  on  the 
top  and  under  side  of  the  belt,  and  securely 
grounded.  Though  this  method  is  fairly  effect- 


ing with  the  operatives. 

Another  device,  which  has  found  considerable 
favor  in  many  mills,  consists  of  a  small  motor 
generator  set  with  transformer.  The  current  is 
transmitted  to  two  inductor  bars,  extending 
across  the  width  of  the  machine,  and  about  three 
inches  above  the  moving  bands  of  paper,  silk  or 
wool  threads.  These  inductor  bars  have  several 
fine  wire  points  which  carry  the  electric  charge. 

Since  these  points  are  charged  by  alternating 
current,  they  carry  both  positive  and  negative 
charges.  Consequently  it  makes  no  difference 
which  of  the  two  kinds  the  hostile  charge  may 
be,  as  it  will  be  neutralized  by  an  opposite  charge 
from  the  wire  points. 


81 


The  cheapest  and  perhaps  simplest  way  to 
overcome  the  harmful  effects  on  incandescent 
lamps  is  to  form  a  protection  for  each  individual 
lamp  unit.  This  is  easily  accomplished  by  means 
of  a  wire  guard  around  the  lamp.  As  the  pur- 
pose of  the  guard  is  to  neutralize  the  static  flux 
before  it  can  collect  on  the  lamp,  it  is  evident 
that  the  smaller  the  meshes  the  more  effective 
it  will  be,  though,  of  course,  they  must  not  be  so 
small  as  to  noticeably  reduce  the  amount  of 
light  from  the  lamp.  Where  several  lamps  are 
combined  in  one  cluster  the  same  result  can  be 
obtained  by  using  one  bowl  shaped  wire  guard 
underneath. 

The  wire  guard  can  be  grounded  by  means  of 
a  wire  extending  up  along  the  fixture  to  some 
iron  work  in  the  building,  or  to  a  nearby  gas  or 
water  pipe  that  will  make  a  good  ground.  This 
wire,  when  intertwined  in  the  lamp  cord,  should 
be  heavily  insulated,  in  order  to  avoid  any  possi- 
ble short  circuit.  A  three  wire  lamp  cord  would 
be  very  satisfactory  for  this  arrangement,  the 
third  wire  being  used  on  the  lamp  guard.  By 
using  a  wire  guard  which  fastens  to  the  bulb  of 
the  lamp  there  will  be  no  metal  connections  be- 
tween the  socket  and  the  grounded  guard, 
thereby  making  this  entire  arrangement  strictly 
in  accordance  with  the  underwriters1  rules. 


Fixtures 

The  selection  of  fixtures  in  an  installation  de- 
pends on  the  surroundings  and  no  set  rules  can 
be  given  to  govern  the  selection.  When  we 
consider  that  in  a  successful  installation  of  an 
artistic  or  decorative  nature  the  fixtures  and 
illuminants  must  blend  so  well  with  the  general 
scheme  that  attention  is  not  attracted  to  them, 
and  a  person  having  left  the  room  is  unable  to 
describe  the  lighting  fixtures,  we  can  readily  see 
that  the  designer  must  have  had  a  considerable 
sense  of  harmony.  The  manufacturers  of  elec- 
trical equipment  have,  in  the  last  ten  years, 
made  rapid  strides  in  the  development  of  a  great 
variety  of  designs.  There  is  a  wide  range  from 
the  plain  designs  of  cheap  tubing  to  the  more 
expensive  ornamental  designs,  but  there  is  a 
wider  range  within  the  latter  class  itself.  The 
use  of  fixtures,  however,  is  often  a  source  of 
danger,  unless  the  proper,  precautions  are  ob- 
served. The  National  Board  of  Fire  Underwriters 
has  laid  down  strict  rules  regarding  the  use  of 
fixtures  which  are  given  in  the  National  Electric 
Code  on  Page  110. 


82 


Visual  Acuity 

Visual  acuity  is,  in  its  broad  sense,  as  the  name 
implies,  acuteness  of  vision.  It  may,  however,  be 
better  understood  by  a  study  of  the  means  used 
to  measure  this  acuteness  of  vision.  Fechner 
performed  a  series  of  experiments,  in  which  he 
varied  the  intensity  of  a  shadow  on  an  illu- 
minated background,  and  determined  the  mini- 
mum difference  in  illumination  distinguishable. 
He  expressed  this  difference  in  illumination  in 
the  form  of  a  ratio,  and  this  latter  became  known 
as  Fechner \s  constant,  and  is  a  basis  of  visual 
acuity  measurements.  This  constant  is  1/101  and 
it  means  that  when  \ve  have  a  1%  difference  of 
intensity  we  can  just  distinguish  this  difference  in 
intensity,  provided  the  two  surfaces  illuminated 
are  in  juxtaposition,  and  can  be  seen  simul- 
taneously. The  constant  does  not  hold  good  for 
very  low  or  very  high  intensities. 

Any  object  focused  in  the  retina  of  the  eye  sub- 
tends a  certain  angle  at  the  eye,  and  from  this 
angle  and  the  focal  length  of  the  eye  may  be  de- 
termined the  size  of  the  image  on  the  retina. 
Helmholz  conducted  a  series  of  experiments  to 
determine  the  smallest  visual  angle  and  the  size 
of  the  focused  image.  Later  this  work  was  sup- 
plemented by  Snellen,  and  the  results  of  his 
investigations  embodied  in  the  reading  chart 
bearing  his  name.  Snellen  determined  that 
the  smallest  visual  angle  for  the  average  eye  was 
one  minute,  and  on  this  basis  he  built  letters 
giving  the  distance  at  which  the  normal  eye 
should  just  perceive  them.  For  instance,  we  find 


E 


for  the  above  letter  "E"  the  normal  reading  dis- 
tance is  20  ft.  In  this  letter  we  have  vertically  two 
spaces  and  three  lines  ;  each  space  and  line  must 
subtend  an  angle  of  one  minute  at  20  feet  or  the 
entire  letter  subtend  an  angle  of  five  minutes. 
Now,  if  a  person  can  just  distinguish  this  letter  at 
21  feet  we  say  he  has  a  visual  acuity  of  21/20,  or 
1.05,  and  we  have  another  means  of  measuring 
acuteness  of  vision.  This  is  by  far  the  most 
popular  conception  of  the  term,  and  this  chart  is 
often  used  by  opticians  in  testing  eyes. 

Visual  acuity  is  affected  by  the  intensity  of  the 
light,  the  color  of  the  light,  and  the  condition  of 
the  eye  (Contraction  of  the  pupil);  also  it  is 
affected  by  the  health,  loss  of  sleep,  mental  and 
physical  fatigue  and  fatigue  of  the  eye  itself. 
However,  the  effect  of  fatigue  is  much  less  than 

83 


is  popularly  supposed. 

The  effect  of  variation  on  intensity  may  be 
shown  by  the  following  curve  in  which  acuity  is 
plotted  as  ordinates  and  intensity  of  illumina- 
tion as  abscissae. 


ir? 

f\              ^ 

i  b      c                    d 
Int2nsity 

e  / 

Fig.  29 

a— Total  darkness. 

b— Threshold  point  where  vision  begins,  about 
.00002  (by  Aubert) . 

c— About  2%  foot  candles. 

f — Where  vision  ceases  at  extremely  high  in- 
tensities probably  above  4000  foot  candles. 

The  point  that  should  be  noted  is  the  very 
small  variation  in  acuity  from  c  to  e,  and  it  is  be- 
tween these  points  that  Fechner's  constant  holds 
good,  slight  variations  being  due  to  the  fact  that 
there  is  a  slight  increase  of  the  acuity  up  to  d 
and  a  gradual  falling  off  from  there  to  e. 

The  effect  of  the  color  of  the  light  on  acuity 
has  also  been  thoroughly  established,  but  exact 
values  are  hard  to  obtain  The  fact  that  mono- 
chromatic colored  lights  present  many  difficulties 
in  photometry,  and  are  hard  to  obtain,  probably 
accounts  for  the  scarcity  of  reliable  data.  It  is 
undoubtedly  a  fact,  however,  that  with  high 
candle-powers  the  part  of  the  spectrum  which 
gives  maximum  acuity  is  about  the  orange- 
yellow,  while  with  low  intensities  this  point  shifts 
to  the  yellow-green  part  of  the  spectrum.  This 
shifting  of  the  maximum  acuity  point  was  first 
noticed  by  Purkinje,  and  was  thereafter  known 
as  the  Purkinje  effect.  The  luminosity  curve  for 
the  different  parts  of  the  spectrum  has  been  in- 
vestigated to  quite  an  extent,  and  it  is  probable 
that  the  acuity  follows  this  curve  in  a  general  way. 

Several  experiments  in  acuity  with  the  use  of 
different  illuminants  used  under  different  con- 
ditions have  been  performed  by  Mr.  Ashe,  at 
Harrison,  and  this  data  has  been  published  from 
time  to  time  in  the  various  engineering  periodi- 
cals, and  the  Transactions  of  the  Illuminating 
Engineering  Society. 

In  considering  any  illuminant  or  form  of  illu- 
mination the  visual  acuity  values  obtained  with 
a  certain  foot  candle  intensity  are  by  no  means 
the  final  criterion  by  which  to  judge  any  illumin- 
ant or  installation.  The  aesthetic  side  which  em- 
braces color  adaptability  and  general  appearance 

84 


must  also  be  considered.  Then  too,  we  have  a 
more  technical  side  which  embraces  distribution, 
watts  per  effective  lumens,  etc.,  but  the  fact  still 
remains  that  visual  acuity  is  an  important  factor 
both  in  installation  and  research  work. 

Intrinsic  Brilliancy  of  Light  Sources. 

Louis  BELL,  Ph.  D.       Candle-power 
per  sq.  in. 

Moore  tube 0.3-1.75 

Frosted  incandescent 2-5 

Candle 3-4 

Gas  Flame 3-8 

Oil  lamp - 3-8 

Cooper-Hewitt  lamp 17 

Welsbach  gas  mantle 20-50 

Acetylene 75-100 

Enclosed  A.  C.  arc 75-200 

Enclosed  D.  C.  arc 100-500 

INCANDESCENT  LAMPS 

Carbon  3.5  watts  per  candle 375 

Carbon  3.1  watts  percandle 480 

Gem  2.5  watts  per  candle .- 625 

Tantalum  2.0  watts  per  candle 750 

"Mazda"  1.25  watts  per  candle 875 

"Mazda''  1.15  watts  per  candle 1000 

Nernst  1.5  watts  per  candle. 2200 

Sun  on  horizon 2000 

Flaming  arc 5000 

Open  arc  lamp 10.000-50,000 

Open  arc  crater 200.000 

Sun  30°  above  horizon 500,000 

Sun  at  zenith 600,000 


Luminescence 

Light  in  any  form  is  produced  either  through 
temperature  radiation  or  through  luminescence, 
or  a  combination  of  the  two. 

When  light  is  produced  by  simply  heating  such 
ordinary  material  as  carbon  or  a  metal  to  a  high 
temperature,  the  light  is  said  to  be  produced  by 
temperature  radiation.  Examples  of  this  are 
the  radiation  of  light  from  (a)  heated  carbon 
particles  in  an  ordinary  flame  as  of  a  candle, 
kerosene  lamp,  or  gas  flame,  (b)  the  crater  light 
of  an  open  or  enclosed  carbon  arc,  or  (c)  the 
light  of  an  incandescent  lamp  filament. 

The  term  luminescence  is  applied  to  radiation 
through  more  complex  action,  involving  a 
change  in  the  material.  There  are  a  number 
of  allied  phenomena  included  in  this  class  which 
are  more  or  less  indefinitely  classified  and  de- 
fined. 

85 


Phosphorescence  and  Fluorescence  are  per- 
haps the  most  familiar  forms  of  luminescence. 

Phosphorescence  is  the  phenomenon  peculiar 
to  certain  substances  such  as  calcium  sulphide 
•which  gives  off  a  glow  after  having  been  ex- 
posed to  light.  This  is  also  known  as  photo- 
luminescence.  Phosphorescence  is  also  applied 
to  describe  light  which  accompanies  the  slow 
oxidization  of  phosphorus,  although,  this  is 
more  scientifically  designated  as  chemi-lumines- 
cence.  The  light  of  the  fire-fly  is  an  example  of 
chemi-luminescence. 

Fluorescence  refers  to  the  property  of  sul- 
phate of  quinine  and  certain  other  materials  by 
which  they  glow  when  exposed  to  light,  the  light 
emitted  being  of  a  lower  rate  of  vibration  than 
the  impinging  light.  A  common  example  of  this 
is  the  transformation  of  invisible  ultra-violet 
radiation  into  visible  light  by  willamite. 

The  color  of  phosphorescent  and  fluorescent 
light  does  not.  usually  correspond  to  the  usual 
superficial  color  of  the  material.  Moreover,  in 
the  case  of  materials  subject  to  both  phenomena, 
the  fluorescent  color  often  differs  from  the  phos- 
phorescent. 

Luminescence  may  be  induced  by  heat  or 
electric  energy.  The  light  from  a  flaming  arc 
lamp  is  usually  ascribed  to  luminescence  induced 
by  heat  generated  from  the  electric  current.  In 
the  case  of  gas  mantles,  investigators  do  not 
agree  as  to  whether  or  not  luminescence  is  in- 
volved in  the  light  production. 

Electro-luminescence  occurs  in  the  mercury 
vapor  arcs  and  vacuum  tube  light  sources.  Al- 
though heat  is  present,  there  is  reason  to  be- 
lieve that  the  action  takes  place  without  its 
forming  an  intermediate  step. 

Luminescence  is  of  especial  interest  in  connec- 
tion with  the  development  of  new  illuminants, 
since  with  our  present  knowledge  it  seems  to 
offer  the  greatest  possibilities  in  the  way  of  in- 
creased efficiency.  Investigations  of  the  light 
of  the  fire-fly  indicate  an  almost  perfect  effi- 
ciency, although,  its  color  in  high  intensities 
•would  be  rather  disagreeable. 


present,  til  Liiic'itu  iiiumriiciuu-i,   even  it  IL  wcic 

carried  so  far  as  to  make  a  sacrifice  in  color. 


Instructions  for  Ordering  Lamps 

To  avoid  misinterpretation  of  orders  it  is  ad- 
visable that  customers  mention  the  following 
facts  on  each  order:— 

1.  QUANTITY  (number  of  lamps  desired). 

2.  CLASS  (Gem,  or  Mazda). 

3.  SIZE  OF  LAMPS  (in  watts,  whether  40  watt, 
100  watt,  etc.     If  Street  Series  lamps  are  ordered 
give  amperes  and  candle-power.    If  Mazda  minia- 
ture lamps  are  ordered  give  candle=power). 

4.  CIRCUIT  VOLTAGE     (voltage  at  the  lamp 
socket) . 

5.  OPERATING    EFFICIENCY    (whether   High, 
Medium  or  Low) . 

6.  STYLE  OF  BASE  (whether  Medium  Screw, 
Mogul    Screw,   Bayonet  Candelabra,   etc.,   and 
also  the  style  number  of  the  base.     When  lamps 
are    scheduled    as    being    manufactured    with 
skirted  and  unskirted  bases,  as  for  example,  the 
regular  40  watt  Mazda,  the  order  should  distinct- 
ly specify  whether  skirted  or  unskirted  base  is 
desired). 

7.  TYPE  OF  BULB  (whether  Straight,  Round 
or  Tubular)  • 

8.  WHETHER  LAMPS  ARE  DESIRED  CLEAR, 
BOWL  FROSTED  OR  ALL  FROSTED.    If  colored 
lamps  are  desired,  state  color  and  whether  lamps 
should  be  superficially  colored  or  made  of  nat- 
ural colored  glass. 

When  lamps  are  furnished  with  the  single 
voltage  label,  item  No.  5  should  be  omitted. 

Order  Standard  Packages. 

When  ordering  lamps,  customer  should  bear 
in  mind  that  the  manufacturer  stores  the  lamps 
packed  in  standard  packages.  An  order  for 
quantities  less  than  standard  package  incurs 
delay  and  needless  expense  on  account  of  the 
repacking  which  necessarily  has  to  be  done  in 
order  to  supply  a  broken  package. 

It  is  also  to  the  customer's  advantage  to  ad= 
here  to  standard  lamps  listed  in  the  schedules. 
The  large  variety  of  lamps  and  voltage  ranges 
which  are  listed  should  permit  the  selection  of 
lamps  that  will  give  satisfactory  results  under 
any  conditions. 

Whenever  it  becomes  necessary  to  order  spec- 
ial lamps,  the  manufacturer  reserves  the  right 
to  fill  all  such  orders  either  short  or  in  excess  of 
the  exact  quantity  ordered  within  the  limits  of 
10  per  cent.  This  is  necessary  on  account  of  the 
fact  that  it  is  impossible  to  always  produce  an 
exact  quantity  of  any  special  lamp. 

If  the  above  directions  are  carefully  followed 
when  orders  are  placed,  needless  errors  and  de- 
lays will  be  avoided. 

87 


Predominating  Color  of  Light  from 
Various  Sources. 

Illuminant  Color 

Average  Daylight  White 

High  sun  Yellowish  White 

Low  sun  Yellow  to  orange  red 

Sky  light  Bluish  white 

Arc-D.C.  open  White  slight  yellow  tint 

Arc-D.C.  enclosed,  80V. 

Arc-D.C.  intensified 

Arc-D.C.  enclosed,  150V.  Purplish  or  violet  tint 

Arc-A.C.  enclosed,  75V.   Slight  purple  tint 

Arc-Magnetite  Approximately  white 

Arc-Flame  (yellow 

carbons)  Orange  yellow 

Arc-Flame  (white 

carbons)  Approximately  white 

Arc-Flame  (red  carbons)  Orange  red 
Nernst  Lamp  Yellowish  tint 

Tungsten- (1.25  wpc.)        Nearly  white,  slight 

yellow  tint 

Incandescent  (carbon)     Yellow  tint 
Acetylene  flame  Yellow  tinted 

Mercury  arc  Blue  green 

Gas  Mantle  Greenish  white  or  amber 

Gas,  ordinary  burner       Pale  orange  yellow 
Kerosene  Orange  yellow 

Cs.,idle  Orange 

Moore  Tube  (COa)  Approximately  white 

Moore  Tube  (NTs)  Salmon  pink 


88 


Electric  Circuits 

With  Special  Reference  to  Incandescent  Lamps 


There  are  two  distinct  systems  for  distributing 
electrical  energy;  namely,  series  and  parallel  sys- 
tems. The  former  is  known  as  the  constant 
current  system  and  the  latter  as  the  constant 
potential.  A  combination  of  the  above  systems 
is  used  for  sign  lighting  and  is  known  as  the 
parallel  group  in  series,  or  simply  the  parallel 
series  method  of  distribution. 

Series  System 

In  the  series  system,  the  same  current  flows 
through  all  the  lamps  and  is  usually  maintained 
at  a  fixed  value  by  a  regulator  or  a  constant 
current  transformer,  as  used  in  alternating  cur- 
rent circuits.  In  this  system,  the  voltage  of  the 
generator  or  transformer  directly  supplying  en- 
ergy to  the  system  is  divided  according  to  the 
resistance  of  the  lamps.  If  all  the  lamps  have 
the  same  rating  and  there  are  ten  lamps  in  a 
series  circuit  of  100  volts,  then  there  is  a  voltage 
of  100  volts  divided  by  10  lamps  or  10  volts  across 
the  terminals  of  each  lamp. 

For  series  systems  all  lamps  should  have  ap- 
proximately the  same  current  rating.  Lamps 
are  cut  out  of  a  series  system,  not  by  turning  off 
the  lamp,  that  is,  by  opening  the  socket,  but  by 
short-circuiting  the  lamp  to  be  cut  out  of  the 
system. 

In  an  incandescent  series  system  each  lamp 
socket  is  equipped  with  an  automatic  cut-out 
which  short  circuits  the  filament  of  the  lamp 
in  case  of  failure  or  burnout.  A  thin  insulating 
film,  wrhich  will  puncture  under  a  potential  of  75 
to  100  volts,  but  which  withstands  lower  volt- 
ages is  placed  between  two  contact  points. 
When  a  lamp  circuit  is  broken  the  full  feeder 
voltage  is  impressed  upon  the  contact  points, 
breaking  down  the  insulating  film,  thereby  re- 
storing the  circuit  by  bridging  the  filament. 

With  alternating  current  the  constant  current 
transformer  supplying  the  current  is  usually  de- 
signed so  as  to  maintain  the  current  constant 
under  all  conditions  independent  of  the  number 
of  lamps  in  the  circuit. 


Parallel  System 

In  this  system  the  voltage  is  approximately 
constant  and  the  current  is  divided  between  the 
lamps  according  to  their  resistance.  This  is 
called  the  parallel  system  because  the  lamps 

89 


are  used  in  parallel  or  multiple.  This  system  is 
used  almost  exclusively  for  interior  lighting. 
The  100-130  volt  lamps  operate  at  a  better  effi- 
ciency than  200-260  volt  lamps,  so  that  on  a  200- 
volt  circuit  2-100  volt  lamps  are  used  in  series  in- 
stead of  1-200  volt  lamp.  This  scheme,  however, 
has  two  disadvantages;  first,  if  one  lamp  fails 
the  circuit  is  open  and  both  lamps  are  out  of 
service;  second,  the  lamps  used  in  series  must 
have  approximately  the  same  current  and  volt- 
age ratings,  as  it  is  impossible  to  satisfactorily 
operate  lamps  of  different  wattages  in  series. 

The  advantage,  however,  of  the  200-volt  system 
is  that  for  the  same  energy  transmitted  the  cur- 
rent is  halved  so  that  the  amount  of  copper 
necessary  for  the  installation  is  quartered,  there- 
by securing  great  economy  in  construction.  To 
make  use  of  this  advantage  and  to  do  away 
with  the  disadvantage  of  two  lamps  in  series  the 
Edison  Three-Wire  System  was  designed.  By 
this  scheme  two  generators  in  series  supply 
power  to  the  outside  wires.  The  lamps  are  con- 
nected between  these  outside  wires  and  the 
middle  or  neutral  wire,  which  is  connected  be- 
tween the  two  generators.  Now  the  burning 
out  of  a  lamp  on  one  side  does  not  materially 
effect  the  lamps  on  the  other  side  since  the  cur- 
rent returns  to  the  neutral  wire  and  maintains  a 
circuit.  When  this  system  is  properly  balanced, 
the  neutral  wire  carries  very  little  current,  and 
therefore  can  be  smaller  in  diameter,  thus  secur- 
ing greater  economy. 

Three=Wire  System  with  Balancer 

This  system  has  a  decided  advantage  over  a 
three-wire  system  supplying  energy  by  two  gen- 
erators in  series,  inasmuch  as  1-200  volt  gen- 
erator can  be  employed.  Between  the  outside 
mains  is  connected  two  dynamos  of  100  volts 
each,  the  two  machines  being  in  series,  the  neu- 
tral wire  being  connected  between  these  ma- 
chines. 

In  case  more  lamps  are  operating  on  one  side 
of  the  system  than  the  other  the  voltage  on  the 
side  which  has  the  most  lamps  in  operation 
tends  to  fall  off,  but  is  automatically  maintained 
by  the  current  flowing  along  the  neutral  wire 
to  one  machine  running  as  a  generator ,  and  there- 
by boosting  the  voltage  of  the  loaded  side  enough 
to  make  up  for  the  voltage  drop  caused  by  the 
unbalanced  conditions.  The  reverse  will  be 
true  if  the  system  becomes  unbalanced  by  more 
lamps  being  operated  on  the  other  side.  By  care- 
fully balancing  the  two  sides  of  this  system  the 
load  will  not  vary  more  than  8  or  10%,  so  that 
the  capacity  of  the  motor  generator  set  will  only 
be  about  8  or  10%  of  the  capacity  of  the  main 
generator  supplying  the  energy  of  the  circuit. 


90 


Voltage  Regulation 

In  maintaining  the  voltage  at  the  lamp  to  a 
fairly  constant  value  it  is  necessary  that  the 
group  of  lamps  employed  be  as  near  the  point  of 
distribution  as  possible  and  that  the  diameter  of 
the  wire  be  large  enough  to  carry  the  current 
without  a  very  large  drop  in  voltage.  A  formula 
is  given  on  page  99  for  calculating  the  drop  in 
voltage  between  the  lamps  and  the  point  of  dis- 
tribution. The  factors  which  determine  the 
sizes  of  wire  are: 

First;  the  wire  must  be  large  enough  to  carry 
the  desired  current  without  overheating  and 
injuring  the  insulation. 

Second;  the  wire  must  be  large  enough  to 
keep  the  voltage  at  the  lamps  within  certain 
limits.  A  total  drop  of  5%  is  permissible;  2%  in 
the  mains  and  3%  in  the  distributing  wires. 

In  a  system  where  power  is  fed  at  the  end  of 
the  system  the  lamps  are  arranged  in  parallel. 
In  this  system  the  voltage  drop  is  great,  inas- 
much as  the  load  center  is  far  from  the  point  of 
distribution,  and  the  current  has  to  traverse  a 
large  amount  of  copper.  It  is  also  necessary  to 
have  a  wire  of  large  diameter  to  prevent  ex- 
cessive drop. 

A  method  for  maintaining  a  constant  voltage 
at  the  lamps  but  which  requires  more  copper  is 
the  return  loop  system.  In  this  system  each 
lamp  receives  approximately  the  same  voltage, 
inasmuch  as  the  current  to  each  lamp  has  to 
traverse  the  same  amount  of  copper  conductor. 
This  is  a  great  advantage  in  all  extensive  in- 
teriors, for  when  lamps  are  installed  they  can  be 
selected  for  the  same  voltage  and  there  is  no 
fear  that  a  lamp  on  the  top  floor  of  a  very  tall 
building  would  receive  a  lower  voltage  than  on 
the  lower  floor.  A  system  of  this  type  installed 
in  one  of  the  prominent  tall  buildings  of  New 
York  City  on  voltage  survey  showed  a  drop  of 
less  than  2%  on  a  200-volt  system  and  the  volt- 
age was  fairly  constant  over  the  entire  building. 


The  Conversion  of  Two=Wire  High 
Voltage  Systems  to  Three=Wire 
y^  Low  Voltage  Systems. 


Due  to  the  better  performance  and  greater 
economy  gained  by  the  use  of  100-130  volt  lamps 
in  preference  to  the  200-260  volt  types  it  is  often 
desirable  to  change  a  high  voltage  system.  In 
such  a  case  it  is  oiten  inconvenient  and  not  at 


all  practical  to  alter  the  wiring:  of  the  whole 
building.  Recently  such  a  change  was  desired  in 
a  large  building  in  New  York  City.  The  prob- 
lem here  was  simplified  to  a  great  extent  by  the 
plan  of  wiring  then  in  use.  This  plan  is  shown  in 
Fig.  30  and  consisted  of  a  three-wire  system  with 


Fig.  30 


the  two  outside  wires  connected  to  the  negative 
bus-bar  and  the  return  loop  connected  to  the 
positive,  so  that  in  reality  it  was  a  double  two- 
wire  system,  having  a  potential  of  240  volts  be- 
tween the  positive  and  each  of  the  two  negative 
wires.  This  plant  was  changed  over  without 
altering  the  wiring  of  the  building,  by  changing 
the  switchboard  connections  in  the  following 
manner:  A  balancer  set  was  installed  and  what 
was  formerly  the  positive  wire  was  connected  to 
the  neuti  al  of  this  set.  One  of  the  outside  wires 
was  connected  to  the  negative  bus-bar  and  the 


other  to  the  positive.  The  new  connections  are 
shown  in  Fig.  31.  By  this  method  120  volt  lamps 
can  be  used  instead  of  the  240  volt  types.  As  the 
load  is  nearly  balanced,  a  balancer  set  of  small 
capacity  is  used  to  take  care  of  any  fluctuations 
in  either  side  of  the  line. 

Distribution  Systems 
Direct  Current 


Two  Wire 


Fig.  32 
Return  Loop 


Fig.  33 
Three=Wire,  Two  Generators 


Fig.  34 
Balancer  Set 


Pig:.  35 
93 


Storage  Battery  Balancer 


Fig.  36 
Double  Dynamo 


Two  armature 
windings  on  the 
same  core  at- 
tached to  two 
separate  com- 
mutators. 


Fig.  37 
Three  Brush  Dynamo 


This  machine  has 
two  adjacent  north 
poles  and  two  adjacent 
south  poles,  making 
practically  a  bi-polar 
Fig.  38  machine  with  divided 

poles.  The  neutral  brush  is  taken  off  between 
like  poles  where  there  is  very  little  e.  m.  f.  gen- 
erated, reducing  sparking  to  a  minimum. 

Dobrowolsky  System 


Fig.  39 

The  neutral  wire  is  connected  to  the  middle 
point  of  an  induction  coil  which  in  turn  is 
connected  to  two  diametrically  opposite  points 
of  the  winding  of  the  armature.  The  e.  m.  f. 

94 


impressed  on  the  terminals  is  alternating  and 
the  inductance  set  up  in  the  two  halves  of  the 
coil  are  equal,  keeping  the  potential  of  the 
neutral  wire  midway  between  that  of  the  out- 
side wires. 

Three=Wire  System  With  Compound 
Wound  Boosters 


Fig.  40 

The  main  generator  is  sufficiently  over-com- 
pounded to  take  care  of  the  total  drop  in  the 
conductors.  The  boosters  are  also  compound 
wound  and  mechanically  coupled.  An  increase 
of  current  through  the  series  field  coil  of  either 
machine  produces  a  higher  voltage  on  the  loaded 
side,  so  that  the  balance  is  maintained. 

The  three-wire  system  can  be  extended  to  a 
five  or  seven-wire  system,  using  compensator 
sets  or  storage  batteries  for  the  balancers. 

The  table  given  below  shows  the  comparative 
weights  of  copper  required  for  the  different  sys- 
tems to  deliver  the  same  wattage  with  the  same 
drop  in  potential  at  the  receiving  end. 

Ordinary  two-wire  system 1.000 

Three-wire  system ;  all  three  wires  of  same 

size .375 

Three-wire  system;  neutral  one-half  size .313 

Four-wire  system;  all  wires  same  size .222 

Five-wire  system;  all  wires  same  size 156 

Five-wire  system;   three  inside  wires  one- 
half  size .109 

Seven-wire  system;  all  seven  wires  of  same 
size 097 

Table  22  shows  the  carrying  capacity  of  copper 
wire  for  direct  current  circuits. 

Alternating  Current  Systems. 

In  Table  23  is  shown  the  amount  of  copper  re- 
quired by  the  various  systems  as  compared  with 
that  required  for  the  single  phase  two-wire 
system.  The  amount  required  for  the  single 
phase  two-wire  system  is  taken  as  100%.  In  the 
single  phase  three-wire  system  consider  the  po- 
tential between  the  two  outside  wires  as  2  et 
where  e  represents  the  voltage  of  the  two-wire 
system.  Applying  the  rule  that  the  amount  of 
copper  varies  inversely  as  the  square  of  the  volt- 
age, only  one  quarter  the  copper  will  be  needed, 


0    1 

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and  add  to  this  a  neutral  of  the  same  size  as  the 
outside  wires,  making-  a  total  of  37.5%.  In  a 
four-wire  system  the  voltage  between  outside 
wires  is  J  <?,  and  with  neutral  and  outside  wires  of 
equal  size  the  amount  of  copper  required  will  be 
22%.  The  two  phase,  four-wire  system  requires 
100%.  The  two  phase  three-wire  system  requires 
145.7%  when  the  comparison  is  based  on  the 
highest  permissible  voltage,  and  72.9%  when 
based  on  the  minimum  voltage.  The  three 
phase,  three- wire  system  requires  33.3%.  with  a 
full  sized  neutral  or  29.17%  with  the  neutral 
one-half  size.  Phase  relations  are  treated  more 
fully  under  Transformer  Connections  on  page  128. 


23.    Amount  of  Copper  Required  for  Transmis= 

sion  at  a  Given  Loss,  Based  on  Minimum 

Difference  of  Potential. 


SYSTEM 

No.  of 
Wires 

Per  Ceni 

Copper 

Single-Phase 

2 

100 

Single-Phase 

3 

37.5 

Two-Phase,  common  return 

3 

72.9 

Two-Phase 

4 

100 

Three-  Phase 

3 

75 

Three-Phase,  neutral  full  size 

4 

33.3 

Three-Phase,  one-half  size 

1 

2<U7 

24.    Amount  of  Copper  Required  for  Transmis= 

sion  at  a  Given  Loss,  Based  on  Maximum 

Difference  of  Potential. 


SYSTKM 


No.  of 
Wires 


Single  Phase 


Percent 
Copper 


100 


Two-Phase,  with  common  return 

3 

145.7 

Two-Phase 

4 

100 

Three-Phase 

3 

75 

The  following  general  formulae  may  be  used 
to  determine  the  size  of  copper  conductors,  cur- 
rent per  conductor,  volts  loss  in  lines,  and  weight 
of  copper  per  circuit  for  alternating  current 
distribution  systems : 

97 


S3 


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I 

w 

3 
* 

1 
1 

I 


333 


•dg'oi 


Smgle- 
Two-phase  (' 
Three-phase 


g  33£8S 

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S232S8SS888888 


98 


_DXWXK 
Area  of  conductor  in  circular  mils  —  — p  x  F  2 — 

W  X  T 
Current  in  main  conductors  =  - 


Volts  loss  in  lines  ~ 


E 
P  X  E  X  M 


100 

1)2  x  WXK  X  A 
Pounds  copper  required  =  pxE2x  l  000000 

W  —  total  watts  delivered. 

D  =  distance  of  transmission  in  feet  (one  way)  . 

P  —  Line  loss  in  per  cent  of  power  delivered, 

that  is.  of  W. 
E  =  Voltage  between  main  conductors  at  receiv- 

ing end  of  circuit. 
The  values  of  constants  K,  T,  M  and  A  for  alter- 

nating current  are  given  in  Table  25. 
For  continuous  current  :    K  =  2160,  T  =  1,  M  =  1 

A  =  6.04 

Wiring 

The  following  formulae  will  be  found  sufficient 
for  calculating  the  size  of  wire  required  to  carry 
a  given  load  with  a  specified  allowable  voltage 
drop. 

The  resistance  of  ordinary  copper  wire  is  equal 
to  the  length  in  feet  divided  by  the  area  in  cir- 
cular mils  multiplied  by  the  resistance  per  mil 
foot,  which  under  working  conditions  is  10.8 
ohms. 

that  is,  R  =  ~  X  10.8  ohms        (1) 
A 

R  =  Resistance  in  ohms 
/  =  Total  length  in  ft. 
A  =  Area  in  circular  mils 

From  Ohm's  Law,  the  loss  in  volts  (e)  in  a 
conductor  is  equal  to  the  current  (I)  multiplied 
by  the  resistance  (R) 

that  is,  e  =  RI          (2) 

Substituting  the  value  of  R  from  equation  (1) 
in  equation  (2) 


Expressed  in  words,  the  voltage  "drop"  is 
equal  to  the  current  times  the  length  of  the  con- 
ductor times  10.8  divided  by  the  area  in  circular 
mils. 

The  /  in  formula  (3)  is  the  length  of  wire 
measured  both  ways  or  the  entire  circuit,  that  is, 

IX2LX10.8       I  X  LX21.6         ... 
e  =  -  -  -  =  •  --  -  --         (4) 
A  A 

Where  L  is  the  distance  between  the  gen- 
erating and  the  receiving  ends.  Formula  (4)  is 
used  to  find  the  drop  in  a  line  knowing  the  size 

99 


of  wire,  the  current  to  be  carried,  and  the  dis- 
tance. 

If  we  wish  to  find  the  size  of  wire  necessary  to 
carry  a  current  (I)  a  distance  (L)  with  an  allow- 
able voltage  drop  (e),  by  transposing  the  for- 
mula, 


Or  to  determine  the  current  that  may  be  car- 
ried by  a  wire, 


If  it  is  desired  to  find  the  size  of  wire  required 
to  carry  a  certain  number  of  lamps,  substitute 
for  (I)  the  number  of  lamps  (N)  multiplied  by 
the  current  taken  by  each  lamp  (i) 

NXIXLX21.6 

or  A  =  —  (7) 

e 

It  is  sometimes  more  convenient  to  make  the 
calculation  in  terms  of  the  wattage  of  the  lamps 
used, 

WXNXLX21.6 
thenA=:      ~E^— 

Where  W  —  watts  per  lamp,  E  =  circuit  volt- 
age at  lamps  and  e  is  the  voltage  "drop." 

Application  of  Kelvin's  Law 

The  question  of  permissible  voltage  drop  in  a 
circuit  increases  in  importance  as  the  cost  of 
energy  increases.  There  are  so  many  factors  to 
be  taken  into  consideration  that  it  is  impossible 
to  give  a  complete  discussion  in  a  limited  space. 
However,  in  any  installation  the  amount  of 
energy  to  be  transmitted  being'  known,  it  is  an 
easy  matter  to  find  the  average  kilowatt  hours 
wa,sted  in  a  conductor  of  a  given  resistance. 
With  regard  to  the  conductors  it  is  principally  a 
question  of  additional  cost  of  copper,  as  the  other 
construction  charges  are  not  greatly  affected  by 
the  increase  in  size  of  the  conductors. 

In  calculating  the  size  of  wire  to  carry  a  given 
load,  a  simple  application  of  Kelvin's  law  may  be 
used.  The  most  economical  current  density  per 
million  circular  mils  is 


Where  L  =  increase  in  annual  charges  on 
transmission  line  resulting-  from  increasing  the 
weight  of  feeders  one  ton,  and  C  —  increase  in 
annual  operating  cost  and  capital  charges  on  the 
power  station,  resulting  from  increasing  the  out- 
put one  kilowatt,  A  is  a  constant  whose  value  is 

A/  Weight  of  conductors,  Ibs.  per  cu.  in. 
Specific  resistance,  ohms,  per  mil  foot 


I AAAMAMAA/ ' 


For  copper,  A  —  380 

Aluminum,  A  =  165 

To  obtain  the  economical  current  density  it  is 
best  to  make  calculation  using  the  maximum 
possible  value  of  L,  also  calculations  using  the 
minimum  possible  value  of  L.  The  mean  of 
these  calculations  will  give  the  advisable  cur- 
rent density. 

General  Electric  Company  Mercury 
Arc  Rectifiers. 

(P.  D.  WAGONER) 

A  detailed  idea  of  the  operation  of  the  mercury 
arc  rectifier  circuit  may  be  obtained  from  Fig.  41. 
Assume  an  instant  when  the  terminal  H  of  the 
supply  transformer  is 
positive,  the  anode  A  is 
then  positiv  e  and  the  arc 
is  free  to  flow  between  A 
and  B,  B  being  the  mer- 
cury cathode.  Following 
the  directions  of  the 
arrows  still  further  the 
f(P  current  passes  through 
the  load  J,  through  the 
reactance  coil  E  and 
back  to  the  negative  ter- 
minal G  on  the  trans- 
former. A  little  later 
when  the  impressed  elec- 
tromotive force  falls 
below  a  value  sufficient 
to  maintain  the  arc 
against  the  counter  elec- 
tromotive force  of  the 
arc  and  load,  the  react- 
ance E,  which  heretofore 
Fig.  41.  has  been  charging,  now 

discharges,  the  dis- 
charge current  being  in  the  same  direction  as 
formerly.  This  serves  to  maintain  the  arc  in  the 
rectifier  until  the  electromotive  force  of  the 
supply  has  passed  through  zero,  reverses  and 
builds  up  to  such  a  value  as  to  cause  A'  to  have 
a  sufficiently  positive  value  to  start  an  arc  be- 
tween it  and  the  mercury  cathode  B.  The 
discharge  circuit  of  the  reactance  coil  E  is 
now  through  the  arc  A'B,  instead  of  through 
its  former  circuit.  Consequently  the  arc  A'B  is 
now  supplied  with  current,  partly  from  the 
transformer  and  partly  from  the  reactance  coil 
/•;.  The  new  circuit  from  the  transformer  is 
indicated  by  the  arrows  inclosed  in  circles.  The 
amount  of  reactance  inserted  in  the  circuit  re- 
duces the  pulsations  of  the  direct  current  suffi- 
ciently for  all  ordinary  commercial  purposes. 
Where  it  is  advisable  to  still  further  reduce  the 
amplitude  of  the  pulsations,  as,  for  instance,  in 
telephone  work,  this  is  done  with  very  slight 
reduction  in  efficiency  by  means  of  reactances- 

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' 


J5    Spe 

3      vac's 

1 !«! 

ii 

"3  SIS 


§111 

111? 


103 


28,    TABLE  OF 
iN 


COMPARATIVE  SIZES  OF  WIRE  GAUGES 
DEC.MALS  OF  AN  INCH. 


No.  of  Wife  Brown  & 
Gauge      Sharpe 


jAttSik"?    English 

Pn  nrWash-l  nam  or       Le8a' 

ftESg"1*'  Standard 


000000 
00000 

0.58000 
0.51650 

0^4615 
0.4305 

0.500 

u.ouu 

0.464 
0.432 

0000 
000 
00 

046000 
0.40964 
0.36480 

0.3938 
0.3625 
0.3310 

0.454 
0.425 
0.380 

0.400 
0.372 
0.348 

0.454 
0.425 
0.380 

0 

1 

2 

0.32495 
0.28930 
0.25763 

0.3065 
0.2830 
0.2625 

0.340 
0.300 
0.284 

0.324 
0.300 
0.276 

0.340 
0.300 
0.284 

3 

4 
5 

0.22942 
0.20431 
0.18194 

0.2437 
0.2253 
0.2070  ' 

0.259 
0.238 
0.220 

0.252 
0.2.<2 
0.212 

0.259 
0.238 
0.220 

6 

7 
8 

0.16202 
0.14428 
0.12849 

0.1920 
0.1770 
0.1620 

0.203 
0.180 
0.165 

0.192 
0.176 
0.160 

0.203 
0.180 
0.165 

9 
10 
11 

0.11443 
0.10189 
0.09074 

0.1483 
0.1350 
0.1205 

0.148 
0.134 
0.120 

0.144 
0.128 
0.116 

0.148 
0.134 
0.120 

12 
13 
14 

0.08081 
0.07196 
0.06408 

0.1055 
0.0915 
0.0800 

0.109 
0.095 
0.083 

0.104 
0.092 
0.080 

0.109 
0.095 
0.083 

15 
16 
17 

0.05706 
0.05082 
0.04525 

0.0720 
0.0625 
0.0540 

0.072 
0.065 
0.058 

0.072 
0.064 
0.056 

0.072 
0.065 
0.058 

18 
19 
20 

0.04^30 
0.03589 
0.03196 

0.0475 
0.0410 
0.0348  • 

0.049 
0.042 
0.035 

0.048 
0.040 
0.036 

0.049 
0.040 
0.035 

21 
22 

23 

0.02846 
0.02535 
0.02257 

0.0317 
0.0286 

0.0258 

0.032 
0.028 
0.025 

0.032 
0.028 
0.024 

0.0315 
0.0295 
0.0270 

24 
25 
26 

0.02010 
0.01790 
0.01594 

0.0230 
0.0204 
0.0181 

0.022 
0.020 
0.018 

0.022 
0.020 
0.018 

0.0250 
0.0230 
0.0205 

27 
28 
29 

0.01420 
0.01264 
0.01126 

0.0173 
0.0182 
0.0150 

0.016 
0.014 
0.013 

0.0164 
0.0148 
0.0136 

0.01875 
0.01650 
0.00155 

30 
31 
32 

0.01003 
0.00893 
0.00795 

0.0140 
0.0132 
0.0128 

0.012 
0.010 
0.009 

0.0124 
0.0116 
0.0108 

0.01375 
0.01225 
0.01125 

33 
34 
35 

0.00708 
0.00630 
0.00561 

0.0118 
0.0104 
0.0095 

0.008 
0.007 
0.005 

0.0100 
0.0092 
0.0084 

0.01025 
0.00950  • 
0.00900 

36 

37 

38 

0.00500 
0.00445 
0.00396 

0.0090 
0.0085 
0.0080 

0.004 

0.0076 
0.0068 
0.0060 

0.00750 
0.00650 
0.00575 

39 
40 

0.00353 
0.00314 

0.0075 
0.0070 

0.0052 
0.0048 

0.00500 
0.00450 

The  Edison  Gauge  is  the  area  in  circular  mils  divided  by  1000. 
104 


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Watt-Hour  Meters 

The  Watt-hour  meters  on  the  market  at  the 
present  time  are,  in  the  main,  of  two  general 
types,  the  induction  type  and  the  Thomson 
or  motor  type.  There  are  several  makes  includ- 
ing- meters  for  various  conditions  of  service,  but 
the  majority  are  an  adaptation  of  one  or  the 
other  of  these  two  types.  With  this  in  mind,  a 
brief  discussion  is  given  herewith  on  the  theory 
of  each  type. 

The  Induction  Watt-hour  Meter  is  suitable  for 
alternating  current  circuits  only.  In  this  meter 
a  tri-polar  magnet  of  laminated  iron  exerts  a 
driving  torque  on  an  aluminum  disc.  The  two 
positive  lugs  Li  Li  of  the  magnet  are  wound 
with  coarse  wire  to  carry  the  line  current,  and 
the  middle  lug  I>2  is  wound  with  fine  wire,  which 
is  connected  across  the  main  as  shown  in  Fig.  42. 


Fig.  42 

As  before  stated,  this  meter  is  used  on  alternat- 
ing current  circuits.  The  surging  of  the  cur- 
rent back  and  forth  through  the  coils  of  Li  Li 
sets  up  a  changing  flux  in  the  lugs,  producing  in 
turn  a  surging  current  through  the  disc  under 
L,2.  This  in  turn  sets  up  a  changing  flux  in  Li>, 
producing  an  electro-motive-force  equal  to  the 
line  voltage  at  each  instant.  Furthermore,  this 
flux  induces  a  proportional  electro-motive:force 
about  I>2  in  the  disc,  A  current  is  set  up  in  the 
disc  in  the  direction  of  the  induced  electro-mo- 
tive-force and  proportional  to  the  line  voltage  at 
each  instant.  This  current  flowing  under  Li  Li 
causes  the  flux  under  them  to  exert  a  torque  on 
the  disc  which  is  proportional  at  each  instant  to 
both  line  current  and  the  line  voltage,  so  that 
the  driving  torque  is  at  each  instant  propor- 
tional to  the  load  delivered  to  the  receiving  cir- 
cuit. The  motion  of  the  disc  is  damped  by  per- 
manent magnets  so  that  the  speed  is  propor- 
tional to  the  driving  torque.  The  total  work 
delivered  to  the  receiving  circuit  is  registered 
on  the  dials  which  are  driven  by  the  spindle  on 
which  the  disc  is  mounted. 

The  Thomson  Watt-hour  Meter  can  be  used 
on  either  direct  or  alternating  current  lines. 
This  meter  (Fig.  43)  is  a  small  electric  motor 
without  iron  parts.  The  field  coils  carry  the  line 

ins 


Shaft  Operating  Dials 




Fig.  43 

current  and  the  armature  is  connected  across 
the  line.  The  speed  of  reduction  is  damped  by 
the  electro-magnetic  drag  upon  the  copper  disc 
caused  by  the  permanent  magnets  DD.  The 
driving  torque  exerted  upon  the  armature  is 
proportional  at  each  instant  to  the  current  both 
in  the  field  coils  and  in  the  armature,  that  is,  it 
is  proportional  both  to  the  line  current  and  to 
the  line  voltage.  The  damping  force  exerted  on 
the  disc  by  the  magnets  is  proportional  to  the 
speed,  so  that  the  total  number  of  revolutions 
on  the  dials  is  always  proportional  to  the  watt- 
hours  of  work  delivered  to  the  receiving  circuit. 


Extracts  from  the  National   Electrical 

Code  as  issued  by  the  National  Board 

of  Fire  Underwriters. 

22.    Incandescent  Lamps  in  Series  Circuit. 

(a)     Conductors  must  be  installed  as  follows1 

1.  Must  have  an  approved  rubber  insulating 
covering:. 

2.  Must  be  arranged  to    enter    and   leave 
the  building  through  an  approved   double-con- 
tact service  switch,  mounted  in  a  non-combusti- 
ble case,  kept  free  from  moisture,  and  easy  of 
access  to  police  or  firemen. 

3.  Must  always  be  in  plain  sight,  and  never 
encased,  except  when  required  by  the  Inspec- 
tion Department  having  jurisdiction. 

4.  Must  be  supported  on  glass  or  porcelain 
insulators,  which  separate  the  wire  at  least  one 
inch  from  the  surface  wired  over  and  must  be 
kept  rigidly  at  least  eight  inches  from  each  other, 
except  within  the  structure  of  lamps,  on  hanger- 
boards  or  in  cut-out  boxes,  or  like  places,  where 
a  less  distance  is  necessary. 

5.  Must,  on  side  walls,  be  protected  from 
mechanical  injury  by  a  substantial  boxing,  re- 
taining an  air  space  of  one  inch  around  the  con- 
ductors,  closed  at  the  top    (the  wires  passing 
through  bushed  holes) ,  and  extending  not  less 
than  seven  feet  from  the  floor.    When  crossing 
floor  timbers  in  cellars,  or  in  rooms  where  they 
might  be  exposed  to  injury,  wi^es  must  be  at- 
tached by  their  insulating  supports  to  the  under 
side  of  a  wooden  strip  not  less  than  one-half  an 
inch    in    thickness.      Instead   of   the    running- 
boards,  guard  strips  on  each  side  of  and  close  to 
to  the  wires  will  be  accepted,    These  strips  to 
be  not  less  than  seven-eighths  of  an  inch   in 
thickness  and  at  least  as  high  as  the  insulators. 

(b)  Kach  lamp  must  be  provided  with  an 
automatic  cut-out. 

(c)  Each  lamp  must  be  suspended  from  a 
hanger-board  by  means  of  rigid  tube.    Hanger- 
board  (73)  must  be  so  constructed  that  all  wires 
and  current-carrying  devices  thereon  will  be  ex- 
posed   to   view    and   thoroughly    insulated    by 
being    mounted  on  a  non-combustible  non-ab- 
sorptive insulating  substance.    All  switches  at- 
tached to  the  same  must  be  so  constructed  that 
they  shall  be  automatic  in  their  action,  cutting 
off  both  poles  to  the  lamp,  not  stopping  between 
points  when  started  and  preventing  an  arc  be- 
tween points  under  all  circumstances. 

(d)  No  electro-magnetic  device  for  switches 
and  no  multiple-series  or  series-multiple  system 
of  lighting  will  be  approved. 

(e)  Must  not  under  any  circumstances  be 
attached  u>  gas  fixtures. 

110 


23.    Automatic  Cut  outs. 

(d)  Must  be  so  placed  that  no  set  of  incan- 
descent lamps,  requiring  more  than  660  watts, 
whether  grouped  on  one  fixture  or  on  several 
fixtures  or  pendants,  will  be  dependent  upon  one 
cut-out. 

Special  permission  may  be  given  in  writing  by 
the  Inspection  Department  having  jurisdiction, 
for  departure  from  this  rule,  in  the  case  of  large 
chandeliers.  (For  exceptions,  see  rule  on  thea- 
ter wiring).  All  branches  or  taps  from  any 
three-wire  system  which  are  directly  connected 
to  lamp  sockets  or  other  translating  devices, 
must  be  run  as  two-wire  circuits,  if  the  fuses  are 
omitted  in  the  neutral,  or  if  the  difference  of  po- 
tential between  the  two  outside  wires  is  over  250 
volts,  and  both  wires  of  such  branch  or  tap  cir- 
cuits must  be  protected  by  proper  fuses. 
25.  Electric  Heaters. 

It  is  often  desirable  to  connect  in  multiple 
with  the  heaters  and  between  the  heater  and  the 
switch  controlling  same,  an  incandescent  lamp 
of  low  candle-power,  as  it  shows  at  a  glance 
whether  or  not  the  switch  is  open,  and  tends  to 
prevent  its  being  left  closed  through  oversight- 

(a)  Must  be  protected  by  a  cut-out  and  con- 
trolled by  indicating  switches.     Switches  must 
be  double  pole   except  when   the    device    con- 
trolled does  not  require  more  than  660  watts 
of  energy. 

(b)  Must  never  be  concealed,  but  must  at 
all  times  be  in  plain  sight.     Special  permission 
may  be  given  in  writing  by  the  Inspection  De- 
partment having  jurisdiction  for  departure  from 
this  rule. 

(c)  Flexible  conductors  for  smoothing  irons 
and  sad  irons,  and  for  all  devices  requiring:  over 
250  watts  must  have  an  approved  insulation  and 
covering. 

(d)  For  portable  heating  devices  the  flexi- 
ble  conductors  must  be  connected  to  an  ap«= 
proved  plug  device,  so  arranged  that  the  plug 
will  pull  out  and  open  the  circuit  in  case  any 
abnormal  strain  is  put  on  the  flexible  conductor. 
This  device  may  be  stationary,  or  it  may  be 
placed  in  the  cord  itself.    Th  e  cable  or  cord  must 
be  attached  to  the  heating  apparatus  in  such 
manner  that  it  will  be  protected  from  kinking, 
chafing  or  like  injury  at  or  near  the  point  of 
connection. 

(e)  Smoothing  irons,  sad  irons  and  other 
heating  appliances  that  are  intended  to  be  ap- 
plied to  inflammable  articles,  such  as  clothing, 
must  conform  to  the  above  rules  so  far  as  they 
apply.    They  must  also  be  provided  with  an  ap- 
proved stand,  on  which  they  should  be  placed 
when  not  in  use. 

(f)  Stationary  electric  heating  apparatus, 

111 


such  as  radiators,  ranges,  plate  warmers,  etc., 
must  be  placed  in  a  safe  location,  isolated  from 
inflammable  materials,  and  be  treated  as  sources 
of  heat. 

Devices  of  this  description  will  often  require  a 
suitable  heat-resisting  material  placed  between 
the  device  and  its  surroundings.  Such  protec- 
tion may  best  be  secured  by  installing  two  or 
more  plates  of  tin  or  sheet  steel  with  a  one-inch 
air  space  between  or  by  alternate  layers  of  sheet 
steel  and  asbestos  with  a  similar  air  space. 

(g)     Must  each  be  provided  with  name-plate, 
giving  the  maker's  name  and  the  normal  capac- 
ity in  volts  and  amperes. 
31.    Sockets. 

(For  construction  of  Sockets  see  No.  72). 

(a;  In  rooms  where  inflammable  gases  may 
exist,  the  incandescent  lamp  and  socket  must  be 
enclosed  in  a  vapor-tight  globe  and  supported 
on  a  pipe-hanger,  wired  with  approved  rubber- 
covered  wire  soldered  directly  to  the  circuit. 

(b)  In  damp  or  wet  places  "waterproof" 
sockets  must  be  used.    Unless  made  upon  fix- 
tures they  must  be  hung  by  separate  stranded 
rubber-covered  wires  not  smaller  than  No.   14 
B  &  S  gauge,  which  should  preferably  be  twisted 
together  when  the  pendant  is  over  three  feet 
long. 

These  wires  must  be  soldered  directly  to  the 
circuit  wires  but  supported  independently  of 
them. 

(c)  Key  sockets  will  not  be  approved  if  in- 
stalled over  specially  inflammable  stuff,  or  where 
Exposed  to  flyings  of  combustible  material. 

Flexible  Cord. 

(For  construction  of  Flexible  Cord  see  No.  54) . 

(a)  Must  have  an  approved  insulation  and 
covering. 

(b)  Must  not,  except  in  street  railway  prop- 
erty, be  used  where  the  difference  of  potential 
between  the  two  wires  is  over  300  volts. 

(c)  Must  not  be  used  as  a  support  for  clus- 
ters. 

(d)  Must  not  be  used  except  for  pendants, 
wiring  of  fixtures,  portable  lamps  or  motors,  and 
portable  heating  apparatus. 

For  all  portable  work,  including  those  pend- 
ants which  are  liable  to  be  moved  about  suffi- 
ciently to  come  in  contact  with  surrounding 
objects,  flexible  wires  and  cables  especially  de- 
signed to  withstand  this  severe  service  must  be 
used. 

When  necessary  to  prevent  portable  lamps 
froni  coming  in  contact  with  inflammable  ma- 
terials, or  to  protect  them  from  breakage,  they 
must  be  surrounded  with  a  substantial  wire 
guard. 

(e)  Must  not  be  used  in  show  windows  or 


112 


show  cases  except  when  provided  with  an  ap= 
proved  metal  armor. 

(f)  Must  be  protected  by  insulating  bush- 
ings where  the  coixi  enters  the  socket. 

(g)  Must  be  so  suspended  that  the  entire 
weight  of  the  socket  and  lamp  will  be  borne  by 
some  approved  method  under  the  bushing  in  the 
socket,    and   above  the  point   where    the  cord 
conies  through  the  ceiling  block  or  rosette,  in 
order  that  the  strain  may  be  taken  from   the 
joints  and  binding  screws. 

37.     Decorative  Lighting  Systems. 


Systems  of  Decorative  Lighting,  provided  the 
difference  of  potential  between  the  wires  of  any 
circuit  shall  not  be  over  150  volts  and  also  pro- 
vided that  no  group  of  lamps  requiring  more 
than  1,320  watts  shall  be  dependent  on  one  cut- 
out. 
71.  Rosettes. 

Ceiling  rosettes,  both  fused  and  f  useless, 
must  be  constructed  in  accordance  with  the  fol- 
lowing specifications: — 

(a)  Base. 

Current  carrying  parts  must  be  mounted  on 
non-combustible,  non-absorptive,  insulating 
bases.  There  should  be  no  openings  through 
the  rosette  base  except  those  for  the  supporting 
screws  and  in  the  concealed  type  for  the  conduc- 
tors also,  and  these  openings  should  not  be  made 
any  larger  than  necessary. 

There  must  be  at  least  one-fourth  inch  space, 
measured  over  the  surface,  between  supporting 
screws  and  current-carrying  parts.  The  sup- 
porting screws  must  be  so  located  or  counter- 
sunk that  the  flexible  cord  cannot  come  in  con- 
tact with  them. 

Bases  for  the  knob  and  cleat  type  must  have 
at  least  two  holes  for  supporting  screws;  must 
be  high  enough  to  keep  the  wires  and  terminals 
at  least  one-half  inch  from  the  surface  to  which 
the  rosette  is  attached,  and  must  have  a  porce- 
lain lug  under  each  terminal  to  prevent  tlie 
rosette  from  being  placed  over  projections  which 
would  reduce  the  separation  to  less  than  one- 
half  inch. 

Bases  for  thet  moulding  and  conduit  box 
types  must  be  high  enough  to  keep  the  wires 
and  terminals  at  least  three-eighths  of  an  inch 
from  the  surface  wired  over. 

(b)  Mounting. 

Contact  pieces  and  terminals  must  be  secured 
in  position  by  at  least  two  screws,  or  made  with  a 
square  shoulder,  or  otherwise  arranged  to  pre- 
vent turning. 

The  nuts  or  screw  heads  on  the  under-side  of 


the  base  must  be  countersunk  not  less  than  one- 
eighth   of  an  inch  and  covered  with  a  water- 
proof compound  which  will  not  melt  below  150 
degrees  Fahrenheit  (65  degrees  Centigrade). 
72.    Sockets. 

(For  installation  rules  see  No.  31.) 

(b)     Ratings. 

Key  Sockets.  — The  standard  key  socket 
(any  socket  haying  Standard  Edison  screw  shell 
and  ordinary  "slow  make"  switch)  to  be  rated 
250  watts,  250  volts. 

Marking  may  be  250  W,,  250  V.  This  rating 
shall  not  be  interpreted  to  permit  the  use,  at  any 
voltage,  of  current  above  2K  amperes  on  any 
standard  key  or  pull  socket. 

A  key  socket  with  Standard  Edison  shell  and 
special  switch  which  "makes"  and  "breaks"  with 
a  quick  snap  and  does  not  stop  when  motion  has 
been  once  imparted  by  the  button  or  handle  may 
be  rated  660  watts,  250  volts  (660  W.,  250  V.) . 

Miniature  and  Candelabra  key  sockets  to  be 
rated  75  watts.  125  volts  (75  W.,  125  V.). 

Keyless  Sockets.— Standard  keyless  sockets 
with  Standard  Edison  screw  shell  to  be  rated  66U 
watts,  250  volts  ( 660  W. .  250  V.) .  This  rating  shall 
not  be  interpreted  to  permit  the  use,  at  any  volt- 
age, of  current  above  6  amperes  on  any  keyless 
socket. 

Weatherproof  sockets  with  Standard  Edison 
shell  and  having  no  exposed  current  carrying 
parts  may  be  rated  660  watts,  600  volts  (600  W., 
600  V.). 

Minature  and  candelabra  keyless  sockets  to 
be  rated  75  watts.  125  volts  (75  W.,  125  V.). 

Double  Ended  Sockets. — Each  Edison  screw 
shell  to  be  rated  at  250  watts,  250  volts  for  key 
type,  660  watts,  250  volts  for  keyless  type,  the  de- 
vices being  marked  with  a  single  marking  apply- 
ing to  each  lamp  holder. 

These  ratings  shall  not  be  interpreted  to  per- 
mit the  use,  at  any  voltage,  of  current  above  2YZ 
amperes  for  key  type,  or  above  6  amperes  for 
keyless  types. 

(g)    Spacing. 

Points  of  opposite  polarity  must  everywhere 
be  kept  not  less  than  three  sixty-fourths  of 
an  inch  apart,  unless  separated  by  a  reliable 
insulation. 

(h;     Connections. 

The  connecting  points  for  the  flexible  cord 
must  be  made  to  very  securely  grip  a  No.  16  or 
18  B.  &  S.  gauge  conductor.  An  up-turned  lug, 
arranged  so  that  the  cord  may  be  gripped  be- 
tween the  screw  and  the  lug  in  such  a  way  that 
it  cannot  possibly  come  out  is  strongly  advised- 

(i)     Lamp  Holder. 

The  socket  must  firmly  hold  the  lamp    in 

114 


place  so  that  it  cannot  be  easily  jarred  out  and 
must  provide  a  contact  good  enough  to  prevent 
undue  heating  with  the  maximum  current  al- 
lowed. The  holding  pieces,  spring  and  the  like, 
if  a  part  of  the  circuit,  must  not  be  sufficiently 
exposed  to  allow  them  to  be  brought  in  contact 
with  anything  outside  of  the  lamp  and  socket. 

(j)    Base. 

The  base  on  which  current  carrying  parts  are 
mounted  must  be  of  porcelain  and  all  insulating 
material  used  must  be  of  approved  material. 

(k)     Key. 

The  socket  key-handle  must  be  of  such  a 
material  that  it  will  not  soften  from  the  heat  of 
a  fifty  candle-power  lamp  hanging  downwards 
from  the  socket  in  air  at  70  degrees  Fahrenheit 
(21  degrees  Centigrade),  and  must  be  securely, 
but  not  necessarily  rigidly  attached  to  the  metal 
spindle  which  it  is  designed  to  turn. 

(1)    Sealing. 

All  screws  in  porcelain  pieces  which  can  be 
firmly  sealed  in  place,  must  be  so  sealed  by  a 
waterproof  compound  which  will  not  melt  below 
200  degrees  Fahrenheit  (93  degrees  Centigrade) . 

(m)     Putting  Together. 

The  socket  as  a  whole  must  be  so  put  to- 
gether so  that  it  will  not  rattle  to  pieces.  Bayo- 
net joints  or  an  equivalent  are  recommended. 

(o)     Keyless  Sockets. 

Keyless  sockets  of  all  kinds  must  comply 
with  the  requirements  for  key  sockets  as  far  as 
they  apply. 

(p)     Sockets  of  Insulating  Material. 

Sockets  made  of  porcelain  or  other  insulating 
material  must  conform  to  the  above  require' 
ments  as  far  as  thev  apply,  and  all  parts  must  be 
strong  enough  to  withstand  a  moderate  amount 
of  hard  usage  without  breaking. 

Porcelain  shell  sockets  being  subject  to 
breakage  and  constitutin  g  a  hazard  when  broken, 
will  not  be  accepted  for  use  in  places  where  they 
would  be  exposed  to  hard  usage. 

<q)     Inlet  Bushing. 

When  the  socket  is  not  attached  to  a  fixture, 
the  threaded  inlet  must  be  provided  with  a 
strong  insulating  bushing  having  a  smooth  hole 
at  least  nine  thirty-seconds  of  an  inch  in  diameter. 
The  edges  of  the  bushing  must  be  rounded  and 
all  inside  fins  removed,  so  that  in  no  place  will 
the  cord  be  subjected  to  the  cutting  or  wearing 
action  of  a  sharp  edge. 

Bushings  for  sockets  having  an  outlet 
threaded  for  three-eighths  inch  pipe  should  have 
a  hole  thirteen  thirty-seconds  of  an  inch  in  di- 
ameter, so  that  they  will  accommodate  approved 
reinforced  flexible  cord. 

115 


STANDARD  SYMBOLS  FOR  WIRING  PLANS 

AS  ADOPTED  AND  RECOMMENDED  BT 

THE.NATIONAL  ELECTRICAL  CONTRACTORS  ASSOCIATION  OF  THE 
UNITED  STATES  AND  THE  AMERICAN  INSTITUTE  Of  ARCHITECTS 
Copies  may  be  had  OD  application  to  the  Sec'  y  of  The  Nat.  Elec.Cunt.Assoti'  u. 
Utica,N.Y.aad  the  Sec'  j-  of  The  Amcric.u  Ingtil.of  Architects,  Washington,  D.C. 

Vjv      Ceiling  Outlet;  Electric  only.     Numeral  in  center  indicates 

**-^>      number  of  Standard  10  C.P.  Incandescent  Lamps. 

}*(i_ Ceiling  Outlet;  Combination,  -i- indicates  4-10  C.P.  Standard 

^       -  Incandescent  Lamps  and  2  Gas  Burners. 

Iff      If  gas  only. 

JJvv      Bracket  Outlet;  Electric  only.    Numeral  in  center  indicates 
%****•      number  of  Standard  10  C.P.  Incandescent  Lamps. 

±  Bracket  Outlet;  Combination.  4  indicates  4-10  C.P.  Standard 
<  2  Incandescent  Lamps  and  2  Gas'liurners. 
|-JK      If  gas  only. 

|_hr|       Wall  or  Baseboard  Receptacle  Outlet.    Numeral  in  center 
pp-*      indicates  number  of  Standard  10  C.P.    Incandescent  Lamps . 

M     Floor  Outlet    Numeral  in  center  indicates  number  of  Standard 
10  C.P.  Incandescent  Lamps. 

_      Outlet  for  Outdoor  Standard  or  Pedestal;  Electric  only. 
*-*6   Numeral  indicates  number  of  Standard  10  C.P.Lamps. 
*gy(Q  Outlet  for  Outdoor  Standard  or  Pedestal;  Combination 
®-J   JL  indicates  0-10  C.P.Standard  Incan.  Lamps;  6  Gas  Burners. 
JDJ     Drop  Cord  Outlet. 
0      Oue  Light  Outlet,  for  Lamp  Receptacle. 
^     Arc  Lamp  Outlet. 

^     Special  Outlet,  for  Lighting,  Heat'ng  and  Power  Current. 
^      as  described  in  Specifications. 
C=OO Ceiling  Fan  Outlet. 


S1  &  P.  Switch  Outlet. 

yj  L>.  P.  Switch  Outlet. 

S:;  3-  Way  Switch  Outlet. 

g>»  4-  Way  Switch  Outlet. 

SD  Automatic  Door  Switch  Outlet 


Show  as  many  Symbols  as  there 
are  Switches.  Or  iu  case  of  a 
very  large  group  of  Switches. 
indicate  number  of  Switches  b\ 
a  Roman  numeral,  thus:  SlXll. 
meaning  12  Single  Pole  Switehe 
Describe  Type  of  Switch^in 
Specifications,  that  is.  Flush  or 
Surface,  Push  Button  or  Snap. 


Electrolier  Switch  Outlet. 
Q      Meter  Outlet. 
flOH  Distribution  Panel. 
$$m&\  Junction  or  Pull  Box. 

J^    Motor  Outlet;  Numeral  ia  center  indicaU-e  Horse  Power. 
[><]  Motor  Control  Outlet. 
=trzt=  Trans  former. 
— —-  — _  Main  or  Feeder  run  concealed  under  Floor. 

Main  or  Feeder  run  concealed  uud^r  Floor  above. 

Main  or  Feeder  run  exposed. 

Branch  Circuit  run  concealed  under  Floor. 

Branch  Circuit  ran  concealed  under  Floor  above. 

•-  Branch  Circuit  run  exposed. 

-••-•--   Pole  Line. 


•  Riser. 

(3  .  Telephone  Outlet:  Private  Service . 

|4  Telephone  Outlet;  Public  Service. 

Q  Bell  Outlet. 

Q/  Buzzer  Outlet. 

02  Push  Button  Outlet;  Numeral  indicates  number  of  Pushed. 

— <£>  Annunciator;    Numeral  indicates  number  of  Points. 

_^  Speaking  Tube. 

-<c)  \YatchmanClockOutlet. 

— J  Watchman  Station  Outlet. 

-@  Master  Time  Clock  Outlet. 

— ([)  Sfc«on<tarj  Time  Clock  Outlet. 

[7]  Door  Oilier. 

H3      Special  Outlet,  for  Signal.  Systems,  as  described  in  Speciticutun^. 

||||||  Battery  Outlet. 

Circuit  for  Clock,  Telephone,  Bell  or  other  Service,  run  un-.U-r 
Floor,  concealed. 

Kind  of  Service  wanted  ascertained  by  Symbol  to  which  line 
connects. 

/  Circuit  for  Clook,  Telephone,  Bell  or  other  Service,  run  under 
I   Floor,  above  concealed. 

*""  |  Kind  of  Service  wanted  ascertained  by  Symbol  to  which  line 
y  connects. 

NOTE:  If  other  than  Standard  1C  C.P.  Incandescent  lamps 
are  desired,  Specifications  should  describe  capacity 
of  Lamp  to  be  used. 

SUGGESTIONS  IN  CONNECTION  WITH  STANDARD 
SYMBOLS  FOR  WIRING  PLANS. 

It  is  important  that  ample  space  be  allowed  1'or  the  in- 
stallation of  mains,  feeders,  branches  and  distribution 
panels. 

It  is  desirable  that  a  key  to  the  symbols  used  accompany 
all  plans 

If  mains,  feeders,  branches  and  distribution  panels 
are  shown  on  the  plans,  it  is  desirable  that  they  be 
designated  by  letters  or  numbers. 

Heights  of  Centre  of  Wall  Outlets(uuless  otherwise  specified ) 
Living  Pvoorag  5  '  0  " 

Chambers  5'  0" 

Offices  G'  0" 

Corridors  0'  z" 

Height   of  Switches  (unless  otherwise  specified) 

4'  0" 

Copyright  1'JOG    )     by  thc  National  Eiectrical  Contractors' 
Copyright  1907    I      Association  of  the  United  States . 


Storage  Batteries 
Principal   Uses 

1.  For  propelling  electrically  driven  'motor 
cars. 

2.  For  ignition  for  gasolene  motors. 

3.  For  railway  train  lighting. 

4.  For  telephone  and  telegraph  work. 

5.  To  carry  the  load  peak  on  a  supply  system. 

6.  To  carry  the  entire  load  during  the  periods 
of  light  demand,  the  generating  equipment  being 
shut  down. 

7.  To  regulate  the  load  on  systems  where 
the  demand  fluctuates  widely. 

8.  To  act  as  an  equalizer  on  three-wire  sys- 
tems in  which    the    generators    are  connected 
across  the  outsides  of  the  system   and  give  a 
corresponding  voltage. 

9.  To  reduce  the  amount  of  copper  required 
for  systems  supplying  variable  loads. 

10.  To  insure  continuous  service. 

11.  As  auxiliaries  to  exciter  dynamos  in  the 
large  alternating  current  stations. 

12.  Combination  of  above  uses  from  4  to  8. 

Lead  Plate  Battery 


2.80 
2.60 

- 

2.40 

^2.00 
1.80 
1.60 
1.40 

1  90 

x 

s 

•-» 

—-• 

^«- 

^L 

Cl 

\tu 

se 

^ 

x"1 

D 

isc 

h;i 

rg 

i 

"***. 

•**, 

x 

\ 

LOO 

\ 

12345678 

Hours  at  No.rmal  Rate 


Fig.  44 

118 


The  lead  plate  storage  battery  is  the  type  now 
in  almost  general  use.  The  negative  plate  is 
composed  of  lead  sponge,  supported  by  a  grid  of 
pure  lead,  and  the  positive  plate  consists  of  lead 
peroxide  supported  in  a  similar  manner.  The 
electrolyte  is  composed  of  dilute  sulphuric  acid 
made  of  sulphur  and  not  from  pyrites  (Fe  82). 
It  need  not  be  chemically  pure  but  must  be  free 
from  chlorine,  nitrates,  copper,  mercury,  arsenic, 
acetic  acid  and  platinum.  The  specific  gravity 
is  generally  specified  by  the  maker  of  the  cell, 
but  should  not  be  less  than  1.150.  The  chemical 
changes  taking  place  when  discharging  are, 
reading  forward  :— 

(1)  PbO2  +  HsSO-t  =  PbSCXt  +  H2O  +  O 

(2)  Pb  +  H2SO4  =  PbSOi  +  H2 

(3)  (1)  +  (2)  =  Pb02  +  Pb  +  2H2SOt  = 


When  reversed,  these  equations  show  the 
changes  occurring  when  the  battery  is  charged. 
The  lead  sulphate  which  is  formed  on  both  plates 
is  a  non-conductor,  and  if  the  cell  is  discharged 
to  a  voltage  of  1.8  per  cell  it  is  extremely  difficult 
to  charge  the  cell  again,  due  to  the  coating  of 
lead  sulphate  on  the  grids.  An  over  discharge 
increases  the  volume  of  the  plates  to  such  an  ex- 
tent that  strains  are  set  up  causing  them  to 
buckle,  or  causing  the  active  materials  to  crack 
and  fall  away.  When  fully  charged  the  voltage 
per  cell  is  about  2.5. 

The  capacity  of  a  storage  battery  is  measured 
in  ampere  hours.  The  charge  and  discharge  rate 
varies  from  6  to  10  amperes  per  square  foot  of 
positive  surface,  not  taking  into  account  the  ad- 
ditional area  obtained  by  ribbing  or  scoring.  A 
cell  of  any  capacity  can  be  obtained  by  assem- 
bling a  number  of  plates  in  parallel.  All  electric 
connections  must  be  made  by  lead  burning. 

The  efficiency  is  the  ratio  of  the  output  to  the 
input  necessary  to  bring  the  cell  back  to  its 
original  condition  after  discharge.  The  efficiency 
of  a  battery  used  to  float  on  a  line  is  about  90  to 
92%,  and  that  of  a  battery  used  independently  is 
about  75  to  80%. 

Rules  for  Operation 

These  rules  or  precautions  regarding  the  use  of 
storage  batteries  are  taken  from  McGraw's 
Standard  Handbook  : 

1.  "Be  sure  that  the  electrolyte  is  free  from 
injurious  impurities. 

2.  '  '  Keep  electrolyte  well  above  tops  of  plates. 

3.  "Maintain  the  specific  gravity  of  the  elec- 
trolyte at  the  density  specified  by  the  manufac- 
turers of  the  battery. 

4.  "Do  not  let  the  density  of  the  electrolyte 
in  any  cell  differ  from  the  standard  density  more 
than  0.05.    Thus  a  cell  having  normal  density  of 
1.200  must  not  register  above  1.205   nor  below 

119 


1.195  when  fully  charged.    Test  each  cell  with 
hydrometer  once  a  week  at  least. 

5.  "Keep  cells  cleaned  out  and  remove  sedi- 
ment when  it  has  deposited  metal  near  the  lower 
edges  of  the  plates. 

6.  "Be  sure  separators  are  all  in  place  and  in 
good  order. 

7.  "Note  any  evidence  of  tank  leakage  and 
correct  at  once. 

8.  "Maintain  insulation  of  cells  from  ground 
and  from  each  other. 

9.  "Begin  charge  immediately  after  the  end 
of  discharge  or  as  soon  thereafter  as  practicable. 

10.  "Do  not  continue  charge  after  the  nega- 
tive plates  begin  to  give  off  gas,  except  the  occa- 
sional "boiling"  to  be  mentioned  in  (14). 

11.  "Never  let  charging  current  fall  below  the 
8-hour  rate  except  toward  the  end  of  charge. 

12.  "Stop  discharge  when  the  battery  poten- 
tial falls  to  1.75  volts  per  cell  with  the  normal  cur- 
rent ;  1.70  volts  per  cell  discharging  at  the  4-hour, 
or  1.60  volts  per  cell  discharging  at  the  1-hour  rate. 

13.  "Watch  the  colors  of  the  plates   and  if 
they  begin  to  grow  lighter  treat  at  once  for  re- 
moval of  sulphate. 

14.  ' ' Give  the  battery  a  prolonged  over-charge 
about  once  a  month.    This  over-charge  should 
continue  at  about  60  per  cent  of  the  8-hour  rate 
until  free  gassing  of  the  negative  plates  has  con- 
tinued for  one  hour. 

15.  "Never  let  the  battery  temperature  rise 
above  110  deg.  F  and,  if  possible,  keep  below 
100  deg.  F. 

16.  "Test  each  cell  once  a  week  with  a  cad- 
mium electrode  and  a  low  reading  voltmeter  to 
determine  the  condition  of  the  negative  plates. 

17.  "Test  the  cells  occasionally  for  drop  on 
discharge  ;  excessive  drop  indicates  the  presence 
of  sulphate,  and  if  the  drop  increases  the  amount 
of  sulphation  is  also  increasing. 

18.  "When  one  of  a  series  of  cells  is  sulphat* 
ed,  charge  it  as  usual  in  series  with  the  others;  on 
discharge  cut  the  cell  out,  connecting  the  opened 
circuit  by  a  heavy  wire  joining  the  two  cells  ad- 
jacent to  the  sulphated  one.     Be  careful  not  to 
short-circuit  the  latter  cell.    When  discharge  is 
ended,  remove  connector  and  switch  in  the  sul- 
phated   cell    so    that  it  again   receives  charge. 
Repeat  this  process  until  the  cell  has  had  its  sul- 
phate fully  reduced.   A  double-pole,  double-throw 
switch  is  conveniently  vised  to  switch  the  cell  and 
the  connector  alternately  into  and  out  of  the 
circuit.    With  it  the  cell  may  be  allowed  to  dis- 
charge a  short  time  before  cutting  out,  which 
improves  the  treatment. 

19.  "Cells  which   stand  a  considerable  time 
unused— say,  as  long  as  45  days — should  work  in 
low  density  electrolyte  not  exceeding  1.210  speci- 
fic gravity  and  be  overcharged  as  directed  (18) . 

120 


It  is  better  to  give  them  a  slight  discharge  and 
charge  about  once  a  week  if  practicable. 

20.  "Cells  which  are  to  be  idle  two  months  or 
more  should  be  taken  out  of  commission  by  first 
fully  charging  and  then  discharging  for  two 
hours  at  the  normal  rate.  Then  draw  off  the  elec- 
trolyte and  fill  the  cells  with  pure  water,  prefer- 
ably distilled.  Begin  discharge  again  at  the 
normal  rate.  The  cells  will  have  to  be  practically 
short-circuited  to  produce  this  discharge  in  the 
water.  When  the  discharge  has  been  carried  to 
a  point  at  which  the  voltage  is  about  0.5  volt  per 
cell,  the  water  is  poured  out  of  the  jars  and  the 
plates  washed  thoroughly  by  putting  a  hose  in 
the  jar  and  flowing  the  water  over  the  plates. 
Allow  the  water  which  fills  the  jars  at  the  end  of 
the  washing  to  remain  24  hours,  then  pour  out 
and  allow  the  electrodes  to  dry.  When  the  bat- 
tery is  to  be  used  again,  pour  in  electrolyte  and 
give  a  prolonged  overcharge." 

Edison  Storage  Batteries 


2345 
Hours  at  Normal  Bate 

Fig.  45 

The  positive  plate  consists  of  one  or  more  per- 
forated steel  tubes,  heavily  nickel-plated,  filled 
with  alternate  layers  of  nickel  hydroxide  and 
pure  metallic  nickel  in  excessively  thin  flakes. 
These  tubes  are  supported  in  a  grid  made  of 
nickel-plated  cold  rolled  steel.  The  negative 
plate  consists  of  a  grid  of  nickel-plated  cold  steel 
holding  a  number  of  rectangular  pockets,  filled 
with  powdered  iron  oxide.  The  plates  are  insu- 
lated from  each  other  and  from  the  containing 


jar,  which  is  of  cold  rolled  sheet  steel,  by  sheets 
of  hard  rubber.  The  electrolyte  consists  of  a 
21%  solution  of  potash  and  distilled  water,  with 
a  small  per  cent,  of  lithia.  The  voltage  per  cell  at 
normal  rate  of  discharge  is  1.2,  and  the  charging 
voltage  should  be  1.85  volts  per  cell.  The 
efficiency  of  the  Edison  cell  ranges  from  60  to  65%. 
There  are  very  few  rules  regarding  the  oper- 
ation of  the  Edison  cell,  The  steel  containers 
should  be  kept  dry  and  clean.  The  plates  should 
be  kept  covered  by  the  electrolyte.  Best  results 
are  obtained  by  charging  at  a  temperature  of  75 
to  85  degrees  F,  and  discharging  at  120  to  125 
degrees  F. 


122 


Transformers 

A  Transformer  is  a  device  for  "  stepping-  up  " 
or  "  stepping  down  "  the  voltage  of  an  alternat- 
ing current  circuit.  The  essential  parts  consist 
of  two  coils,  or  a  multiple  of  two,  wound  upon 
an  iron  core.  An  alternating  e.  m.  f.  is  applied 
to  the  terminals  of  one  coil,  termed  the  primary. 
See  Fig,  47.  The  alternating  current  in  the 
primary  winding  sets  up  an  alternating  mag- 
netic field  in  the  iron  core.  This  alternating 
flux,  cutting  the  secondary  winding,  induces  an 
alternating'  e.  m.  f.  in  this  winding.  The  rela- 
tion between  the  primary  and  secondary  volt- 
ages depends  upon  the  number  of  turns  in  the 
secondary  as  compared  with  those  in  the  prim- 
ary winding.  This  relation  can  be  expressed  as 
follows : 

F/           N' 

E"  ~   N"  ' 

Where  E'  is  the  primary  voltage,  E"  the  sec- 
ondary voltage,  N'the  number  of  primary  turns 
and  N"  the  number  of  secondary  turns. 

The  Shell  Type  Transformer  has  a  double 
magnetic  circuit  with  the  iron  built  up  through, 
and  around  the  coils. 

The  Core  Type  Transformer  has  a  single  mag- 
netic circuit  and  has  the  coils  built  around  the 
legs  of  the  core. 

Core  Loss  is  composed  of  hysteresis  loss  and 
the  eddy  or  Foucalt  loss. 
Hysteresis  Loss 
Wh=n  Vf  BL«  X  10-7 
Wh  =  Watts  loss 

V     r=  Volume  of  iron  core  in  cubic  cm. 
f      =  Frequency  in  cycles  per  second 
B     —  Maximum  flux  density  in  lines  per  sq.  cm. 
n     =  Variable  constant  =  .0021  approx. 
Eddy  Current  Losses 
•  We  =  b  V  f2  t2  B2 

t      =  Thickness  of  laminations  in  cm. 
b     =  Constant  depending  upon  the  specific  re- 
sistance of  iron,  usually  about  1.6  x  10— n 
Values  of  B  in  Maximum  Lines  Per  Sq.  Cm. 
Frequency        1-5  kw.        10-25  kw.        100-500  kw. 
25  7500  6500  5500 

40  6500  6500       .  4500 

60  5000  4500  4000 

100  4000  3500  3000 

120  3500  3000  2500 

Copper  losses  are  composed  of  the  I-R  losses 
in  the  primary  and  secondary  coils.  The  effi- 
ciency of  a  transformer  is  the  ratio  of  its  net 
power  output  to  its  gross  input,  the  output  be- 
ing measured  with  non-inductive  load.  The 

123 


power  input  is  the  sum  of  the  output,  the  core 
loss  and  the  PR  loss  of  the  primary  and  sec- 
ondary coils. 

Regulation  in  transformers  is  the  percentage 
of  fall  in  secondary  voltage  from  no  load  to  full 
load  for  constant  potential  working:.  I>ue  to 
the  increase  of  resistance  the  regulation  in- 
creases with  rise  of  temperature. 

Transformer  Testing  for  Central  Stations 

The  financial  success  or  failure  of  a  lighting 
or  power  plant  is  dependent  on  the  efficiency  of 
the  system.  In  alternating  current  distribution 
the  transformers  are  frequently  scattered  in 
large  numbers  throughout  the  system  and  their 
cumulative  losses  greatly  effect  the  efficiency 
of  the  entire  system.  It  is  therefore  essential  to 
the  self-protection  of  Central  Stations  that  suffi- 
cient tests  are  made  on  the  transformers  to  be 
sure  that  the  guarantees  are  fulfilled.  The  fol- 
lowing tests  can  be  made  without  a  great  outlay 
for  instruments. 
Insulation  Test 


Fig.  46. 

1.  Between  primary  and  all  other  parts. 

2.  Between  secondary  and  all  other  parts. 

3.  Between  turn  sand  sections  of  the  windings. 
The  method  of  connection  is  shown  in  Fig.  46. 

In  applying  the  high  potential  test  to  one  wind- 
ing the  remaining  winding  should  be  carefully 
grounded  to  the  core  and  frame  to  avoid  static- 
ally induced  strains.  All  primary  leads  should 
be  connected  together  as  well  as  secondary 
leads,  in  order  to  secure  throughout  the  winding 
a  uniform  potential  strain  during  the  test. 

1.  Set  the  spark  gap  for  a  voltage  10  per  cent, 
in  excess  of  that  which  is  to  be  applied.     (See 
Table  31), 

2.  By  means  of  the  regulator  on  the  low  volt- 
age side  adjust  the  testing    outfit    to   deliver 
minimum  voltage. 

3.  Connect  the  apparatus  to  be  tested  to  the 
high  voltage  side  of  the  testing  outfit. 

4.  Close  low  voltage  switch  and  gradually  in- 
crease the  voltage  until  the  desired  potential  is 
indicated  on  the  electrostatic  voltmeter. 

5.  Reduce  the  voltage  slowly. 

124 


If  the  insulation  under  test  be  good  there  will 
be  no  difficulty  in  bringing-  the  potential  up  to 
the  desired  value,  provided  the  transformer  be 
of  sufficient  capacity.  If,  however,  the  insula- 
tion be  weak  or  defective  it  will  be  impossible  to 
obtain  a  high  voltage,  and  an  excessive  current 
will  be  indicated  by  the  ammeter.  A  breakdown 
in  insulation  will  result  in  a  drop  in  voltage  in- 
dicated by  the  electrostatic  voltmeter  and  by  an 
excessive  current. 

31.    Standard  Spark  Gap 


Voltage  in 

Kilovolts 

5 

10 

20 

30 

40 

50 

60 

70 

80 

90 
100 
110 
120 
130 
140 
150 


Core  Loss 


< — Ope  a  Circuit-> 
Fig.  47. 


Gap  in 
Inches 

.2 

.5 

1.0 

1.65 

2.50 

3.50 

4.60 

5.85 

7.10 

8.35 

9.50 

10.70 

11.85 

12.98 

14.00 

15.00 


1.  Estimate  the  capac- 
ity   of    the    instruments 
required. 

2.  Connect  the  selected 
instruments  as  shown  in 
Fig.  47  to  the  low  potential 
side  of  transformer  on  test, 
the    high    potential    side 
being     on     open    circuit. 
The     generator     speed 
should  be  observed  by  a 
tachometer    or    speed 
counter    in    case    a   fre- 
quency     meter     is      not 
available. 

3.  Connect  leads   from 
the  transformer  on  test  to 
the  leads  from  the  switch- 
board or  source  of  power 
through  a  double  pole,  sin- 
gle throw  switch. 

125 


4.  'dose  the  switch' and  make  a  preliminary 
reading  of -the  instruments  at  approximately  the 
voltage  and  frequency  required. 

5.  Adjust  the  voltage  and  frequency  of  the 
circuit  as  desired  and  make  simultaneous  obser- 
vations of  the  wattmeter,  voltmeter,  ammeter 
and  frequency  meter. 

6.  Record  the  results  and  note  the  numbers 
of  the  instruments  used  with  their  correspond- 
ing- constants. 

NOTE:    The  generator  should  carry  no  other 
load  during  the  test. 

7.  Calculate  the  losses  in  the  voltmeter  and 
in  the  pressure  coil  of  the  wattmeter  and  sub- 
tract them  from  the  observed  reading  of  the 
wattmeter.     The  result  is  the  core  loss  of  the 
transformer. 

NOTE:    The  loss  in  the  voltmeter  and  in  the 
pressure  coil  of  the  wattmeter  are  equal  in  each 

E2 
case  to  — ,  R  being  the  resistance  of  the  coil  in 

question. 

Measurement  of  Resistance 


Transformer  under  Test 


Fig.  48 

This  method  of  finding  the  resistance  of  a 
transformer  is  simply  an-  application  of  Ohm's 

Law,  that  is,  R  =  y .    Direct  current  is  used  and 

the  connections  are  as  shown  in  Fig.  48.  Simul- 
taneous readings  should  be  taken  on  the  volt- 
meter and  ammeter  at  different  values  of  cur- 
rent. Reduce  the  value  of  resistance  to  standard 
room  temperature  of  25°  C.  using  the  following 
equation: 

Resistance  at  25°  C.  =  R 

R  =  resistance  at  t°  C. 

t  =  temp,  of  transformer  on  test, 

Impedance  Loss 

Impedance  may  be  considered  as  constant  at 
all  loads.  It  is  generally  measured  at  full  load 
current,  and  the  impressed  voltage  is  then 
known  as  the  impedance  volts,  and,  when  ex- 
pressed in  per  cent,  of  the  normal  rated  voltage 
of  the  transformer,  as  the  per  cent,  impedance 
drop. 


126 


Transformer  under  Test 

Fig.  49 
Connections  should  be  as  in  Fig.  49. 

1.  Short  circuit  one  of  the  windings  of  the 
transformer,  preferably  the  secondary. 

2.  Adjust  the  voltage  to  give  full  load  current 
in  the  winding  of  the  transformer;  then  make 
simultaneous  readings  of   the   voltmeter,  am- 
meter and  frequency  meter. 

Record  the  results  and  calculate  the  imped- 
ance. In  the  equation, 

TC 

I==VR2+  (27rnL)2 

the  expression       v/R2-|-(2  *  n  L)~   is'the  im- 
pedance in  ohms. 
Polarity 

When  transformers  manufactured  by  different 
companies  are  to  be  run  in  parallel,  it  is  necessary 
to  test  them  in  order  to  avoid  the  possibility  of 
connecting  them  in  such  a  way  as  to  short-cir- 
cuit the  one  on  the  other. 

A 


Fig.  50 

Refer  to  Fig.  50.  In  the  connections  shown  the 
leads  are  so  brought  out  that  the  primary  and 
secondary  form  a  continuous  winding,  uniform 
in  direction  when  B  and  D  are  connected  to- 
gether. Consequently,  if  with  B  and  1)  con- 
nected a  given  voltage  is  impressed  from  A  to  B 
the  result  of  the  voltage  from  A  to  C  will  be 
more  than  that  impressed  at  A  B  if  the  leads 
have  been  properly  brought  out,  and  less  than 
the  voltage  impressed  at  A  B  if  they  have  not 
been  properly  brought  out. 

127 


Transformer  Connections 
Delta-Delta  Connection 


Delta -Delta 
Fig.  51 

The  voltage  per  transformer  is  the  same  as 
that  between  the  line  wires,  the  current  per 
transformer^  equal  to  the  current  per  line  wire 
divided  by  \/3. 

Star  or  Y  Connection 


Wdv-T 
tTflmrH 


Star  or  Y  Connection 
Fig.  52 

The  current  per  transformer  is  the  same  as 
that  per  line  wire;  the  voltage  per  transformer 
isjiqual  to  the  voltage  between  wires  divided  by 
•S-. 


Delta=Y  Connection 


Delta -Y"  Connection 
Fig.  53 


Y=Delta  Connection 


"  Delta-Connection 
Fig.  54 

128 


T-Connection  (Scott  Transformer) 


'!T"  Connection. 

Fig.  55 

In  this  scheme  the  voltage  impressed  across 
one  transformer  is  only  86.6  per  cent,  of  that  im- 
pressed across  the  other. 
Method  of  Cooling  Transformers 

1.  Self-cooling  dry  transformers. 

2.  Self-cooling  oil  filled  transformers. 

3.  Transformer  cooled  by  forced  current  of 

4.  Transformer  cooled  by  forced  current  of 
water. 

5.  Transformer   cooled   by   combinations    of 
both. 

Limiting  Temperature  Rise 

The  temperature  rise  should  not  exceed  50°  C. 
in  electric  circuits  by  resistance  and  in  other 
parts  by  thermometer. 
Overload  Capacity 

Constant  potential  transformers,  25  per  cent, 
for  two  hours,  except  in  transformers  connected 
to  apparatus  for  which  a  different  overload  is 
guaranteed,  in  which  case  the  same  guarantee 
shall  apply  for  the  transformer  as  for  the  appa- 
ratus connected  thereto. 
Standard  Ratios 

It  is  recommended  that  the  standard  trans- 
former ratios  should  be  applicable  to  the  follow- 
ing voltages,  which  are  standard:  6600;  11,000; 
22,000;  33,000;  44,000;  66,000;  88,000;  110,000. 

The  ratio  will  usually  be  an  exact  multiple  of 
5  or  10. 

Rules  for  Installing  and  Operating 
Tranformers. 

Must  not  be  placed  in  any  but  metallic  or  other 
non-combustible  cases.  Must  be  constructed  to 
comply  with  the  following  tests  : 

1.  Shall  be  run  for  eight  consecutive  hours  at 
full  load  in  watts  under  conditions  of  service,  and 
at  the  end  of  that  time  the  rise  in  temperature, 
as  measured  by  the  increase  of  resistance  of  the 
primary  coil  shall  not  exceed  135°  F. 

2.  The  insulation  of  transformer  when  heated 
shall  withstand  continuously  for  rive  minutes  a 

129 


difference  of  potential  of  10.000  volts  (alternating-) 
between  primary  and  secondary  coils  and  core, 
and  between  the  primary  coils  and  core;  'also 
must  withstand  a  no  load  run  at  double  voltage 
for  30  minutes. 

In  Central  or  sub-stations  the  transformers 
must  be  so  placed  that  the  smoke  from  the  burn- 
ing out  of  the  coils,  or  the  boiling  over  of  the  oil, 
where  oil  filled  cases  are  used,  can  do  no  harm. 

The  neutral  point  of  the  transformer  or  the 
neutral  wire  of  distributing  systems  may  be 
grounded  and  when  grounded  the  following  rules 
must  be  complied  with. 

1.  Transformers    feeding    two  wire    systems 
must  be  grounded  at  the  center  of  the  second- 
ary coils. 

2.  Transformers  feeding  systems  with  a  neut- 
ral wire  must  have  the  neutral  wire  grounded 
at  the  transformer  and   at   least   every   250  ft. 
beyond. 

In  general,  in  order  to  obtain  minimum  operat- 
ing costs,  transformers  of  the  present  standard 
performances  should  be  used  on  a  load  which  will 
bring  them  up  to  the  maximum  safe  tempera- 
ture rise. 

Constant  Current  Transformers 

The  Constant  Current  Transformer  in  its  sim- 
plest type  consists  of  a  core  of  the  double  mag- 
netic circuit  type  with  three  vertical  legs  and 
two  coils  placed  around  the  central  leg.  The 
primary  is  fixed  and  the  secondary  is  suspended 
and  balanced  by  counter  weights  so  that  it  can 
move  up  and  down.  A  flow  of  current  in  the 
coils  causes  a  repulsion  between  them,  causing 
them  to  separate  to  the  position  for  which  they 
are  balanced.  An  increase  of  current  due  to  cut- 
ting out  of  series  lamps,  for  example,  causes  them 
to  separate  farther,  increasing  the  leakage  and 
thereby  cutting  down  the  induction.  With  any 
current  less  than  normal  the  repelling  force 
diminishes,  and  the  primary  and  secondary  coils 
approach  each  other  thereby  restoring  the  cur- 
rent to  its  normal  value. 

The  General  Electric  Company  has  recently 
designed  a  new  edgewise  wound  transformer, 
with  concentric  coils  and  cruciform  core,  giving 
better  efficiency,  higher  power  factor  and  closer 
regulation.  It  is  so  designed  that  the  short  cir- 
cuiting of  the  secondary  at  any  time  will  not 
cause  any  serious  damage.  It  will  regulate  from 
no  load  to  full  load  within  1/10  of  an  ampere, 
above  or  below  normal  rated  current  on  any  pri- 
mary voltage  within  5  per  cent  of  the  normal 
rated  value.  By  means  of  a  slight  adjustment  it 
can  be  adapted  for  any  secondary  current  within 
7  1/2  per  cent  of  normal  rated  value,  thus  allow- 
ing the  customer  to  order  lamps  of  other  than 
exact  standard  values. 

130 


Trigonometric  Functions  and  Rules. 

1.  The  sine  of  an  angle  is  the  ratio  of  the 
opposite  leg  to  the  hypotenuse. 

2.  The  cosine  of  an  angle  is  the  ratio  of  the 
adjacenl  leg  to  the  hypotenuse. 

3.  The  tangent  of  an  angle  is  the  ratio  of  the 
opposite  leg  to  the  adjacent. 

4.  The  cotangent  of  an   angle  is  the  ratio  of 
the  adjacent  leg  to  the  opposite. 

5.  The  secant  of  an  angle  is  the  ratio  of  the 
hypotenuse  to  the  adjacent  leg. 

6.  The  cosecant  of  an  angle  is  the  ratio  of  the 
hypotenuse  to  the  opposite  leg. 

7.  The  versed  sine  of  an  angle  a  is  equal  to  1 
—  cos  a. 

8.  The  coversed  sine  of  an  angle  a  is  equal  to 
1  —  sin  a. 

Sin  x  =:  ---  :     Cos  x  =:  -    ;    Tan  x  =  — 


sin'-  x  -f  cos2  x  =  1  ;     1  +  tan2  x  =  sec-  x  : 
1  -fcot2x  =  csc2x. 

(       TT  I  •        \        n 

COS  X  =  sill     —  -  -- 


--  x    . 

sin  (if  —  x  )  =  sin  x  ;     cos  (*  —  x  )  =  —  cos  x  ; 

tan  (  if  —  x  )  =  —  tan  x 
sin  (  x  -}-  y  )  =  sin  x  cos  y  +  cos  x  sin  y. 
sin  (  x  —  y  )  =  sin  x  cos  y  —  cos  x  sin  y. 
cos  (  x  +  y  )  —  cos  x  cos  y  —  sin  x  sin  y. 

,       .      v         tan  x  -J-  tan  y 
tan  (  x  +  y  )  =  — 

1  —  tan  x  tan  y 

,        tan  x  —  tan  y 

tan  (  x  —  y  )  =  — 

1  +  tan  x  tan  y 

sin  2  x  —  2  sin  x  cos  x;    cos  2  x  =  cos-  x  —  sin2  x  ; 

2  tan  x 

tan  2  x  =  -  -       5  —  . 
1  —  tan2  x 

.      XX  „  X  .     0  X 

sin  x  =  2  sm—  cos  —  :    cos.  x  =  cos2—  —sin2  —  . 

2  tany 


l-tan2y 

cos2  x=— H — r-cos2x;  sin2x=:— —  cos2x. 

131 


1  -f  cosx  =  2  cos'2-^;    1  —  cos  x  =  2  sin2—-. 


!f=±^L£5iI; 


-- 
1  -f  cos  x 

sin  x  +  sin  y  =  2  sin  —  (x  -f  y)  cos—  (x  —  y ) 
sin  x  —  sin  y  =  2  cos^~  (x  +  y)  sin  —  (x  —  y) 
cos  x  -j-  cos  y  =  2  cos—  (x  +  y)  cos  —  (x  —  y) 

cosx  —  cosy  ==  —  2  sin—  (x  -f-  y)  sin—  (x  —  y) 
Law  of  sines 


sin  A     sin  B     sin  C 
Where  A  is  the  angle  opposite  side  a 
B  is  the  angle  opposite  side  b 
C  is  the  angle  opposite  side  c 
Law  of  cosines 

as  rr  b2  +  c2  —  2  be  cos  A 

The  following  table  gives  the  signs  for  the  trigo- 
nometric functions  in  the  various  quadrants : 


Quadrant 

sin 

cos 

tan 

cot 

sec 

CSC 

First 

+ 

+ 

+ 

+ 

+ 

-f 

Second 

+ 

- 

+ 

Third 

— 

+ 

+ 

- 

- 

Fourth 

~    1    + 

— 

— 

+ 

- 

In  the  diagram  below  (Fig.  56)  the  functions 
are  positive  in  quadrants  denoted  by  arrows. 


Mensuration. 

Square  Root 

The  method  of  extracting  square  root  is  best 
shown  by  the  use  of  an  example:  Find  the 
square  root  of  2809,  or,  in  other  words,  find  the 
length  of  the  side  of  a  square  which  contains 
2809  units : 


2  x  50  =  100 

3 

103 


25 


309 


309 


Fig.  57 

First  divide  the  number  into  periods  of  two  fig- 
ures each,  starting  from  the  decimal  point.  The 
square  root  will  have  one  figure  for  each  period 
in  the  square,  so  the  side  of  this  particular  square 
will  be  represented  by  tens,  and  obviously  by  5 
tens  since  the  largest  square  in  28  is  25.  This 
square  subtracted  leaves  309  square  units  to  be 
taken  into  account.  These  309  square  units  can 
be  divided  up  into  three  parts,  consisting  of  two 
strips  B  and  C,  50  units  long  and  a  smaller  square 
D  at  the  corner,  whose  dimensions  we  do  not  yet 
know.  The  combined  length  of  B  and  C  is  2  x  50, 
or  100,  and  100  is  contained  in  309,  3  times.  Now 
assuming  the  width  of  these  strips  to  be  3  the 
area  of  the  strips  will  be  300,  and  that  of  the 
square  will  be  9,  making  a  total  of  309  which 
completes  the  square. 

Rule  to  be  Followed  in  Extracting  the  Square 
Root  of  a  Number. 

Separate  the  number  into  periods  of  two  figures 
each,  beginning  at  the  decimal  point. 

Find  the  greatest  square  in  the  left  hand  period 
and  write  its  root  for  the  first  figure  of  the 
required  root. 

Square  this  root  and  subtract  the  result  from 
the  left  hand  period  and  annex  to  the  remainder 
the  next  period  for  a  dividend. 

Double  the  root  already  found  and  multiply  it 
by  10  for  a  trial  divisor,  and  divide  it  into  the 
dividend,  making  allowance  for  the  fact  that 
the  dividend  must  contain  in  addition  to  the  pro- 
duct of  the  trial  divisor  and  the  quotient  obtained, 
the  square  of  the  quotient  itself.  Subtract  this 
sum  of  the  products  from  the  dividend,  annex  to 
the  remainder  the  next  period,  and  proceed 
as  before. 

CUBE  ROOT 

Rule  to  be  Followed  in  Extracting  the  Cube  Root 
of  a  Number. 

Separate  the  number  into  periods  of  three 
figures  each,  beginning  at  the  decimal  point. 

133 


Find  the  greatest  cube  in  the  left  hand  period 
and  write  its  root  for  the  first  figure  of  the 
required  root. 

Cube  this  root,  subtract  the  result  from  the 
left  hand  period  and  annex  to  the  remainder  the 
next  period  for  a  dividend. 

Take  three  times  the  square  of  the  root  already 
found,  consider  it  as  tens  for  a  trial  divisor  and 
divide  it  into  the  dividend.  The  quotient  or  the 
quotient  diminished  will  be  the  second  part 
of  the  root. 

To  this  partial  divisor  add  three  times  the  pro- 
duct of  the  first  part  of  the  root,  considered  as 
tens  by  the  second  part,  and  also  the  square  of 
the  second  part.  Their  sum  will  be  the  complete 
divisor. 

Multiply  the  complete  divisor  by  the  second 
part  of  the  root  and  subtract  the  product  from 
the  dividend.  Continue  this  until  all  the  figures 
of  the  root  have  been  found. 

Illustration  and  Explanation  of  the  Above  Rule 


Fig.  58 

Find  edge  of  cube  whose  contents  are  13,824  units. 
13824 1 24 

As  there  are  two 
periods  in  this  fig- 
ure the  root  will  be 
in  the  order  of  tens- 
The  largest  cube  in 


-  3X2Q2  — 1200 
(4)  X  1200  =  4800 
(4)  X  4X3  X  20  =  960 


(4) 


=  64 


co?4.       the  first  period  is  8. 
This  subtracted 
from    the    number 
This  remainder  must 


5824 

leaves  5,824  cubical  units. 

be  composed  of  seven  parts,  C,  B,  D,  E,  F,  G 
and  H.  The  sum  of  the  areas  of  the  faces  of  C, 
B  and  D  is  202  X  3  —  1200.  This  is  contained  in 
5,824  four  times.  With  this  as  a  trial  quotient 
we  can  now  find  the  contents  of  the  additional 
parts.  The  contents  of  C,  B  and  D  is  1200  X  4  = 
4800;  of  E,  F  and  G  is  3  (4  X  4  X  20)  =  960;  of  H 
is  4s  —  64,  making  a  total  of  5,824. 

134 


Figr.  j 


135 


Formulae  for  Finding  Area  and  Volumes 
of  Geometrical  Figures. 

Meaning  of  Symbols  Used 

A  =  Area  of  plane  surface 

d  =  Diameter 

R  =  Radius 

V  -  Volume 

p  =  Perimeter 

b  =  Base 

h  —  Altitude 

C  =  Area  of  convex  surface 

S  =  Area  of  entire  surface 

ir  =  3.1416 

Circle 

A   =     7T     R-'  p   —   2     7T     R 

Triangles 

Fig.  a  a  =  V  b2  4-  h2  •  A  =  —  bh 

2 


Fig.  b  c  =  1 

Fig.  c  c  =  1 

jj 

Rectangle 

Fig.  d  A  =  rib 

Paralellogram 

Fig.  e  A  =  hb 

Trapezoid 

Fig.  f  A  =  |-h  (a  +  b) 

Trapezium 

Fig.  g  A—  —  f(h-f-h/)  +  ~he  + 

j  h'  g  =y  [f  (h  +  h')  +  he  -f  h'  g] 
Ellipse 


A=— D  d 


Sector 


Fig.  i  A  =  ~l  R 


A  -          n      -   .008727 


Segment 

Fig.j  A=-|  [/R-c     (R-h)] 


Cylinder 

C=  *  dh 

S  =  2  ir  R  h  -h  2  T  R* 

V=    IT    R2h 

Cone 

C  =  %  TT  d  /  (/  =  Slant  height) 
S  =  IT  R  /  +  TT  R2 
V=  1/3  TT  R2  h 

Sphere 

S  =1  4  TT   R2   —  7T  d- 


Circular  Ring 

r    =  Radius  of  cross  section 
R  =  Mean  radius  of  ring 
S  =  4  »  *  R  r 
V  =  2  T  R  r2 

Frustum  of  a  Cone 

C  =  ^y-  (D  +  d)      (d  =  Diameter  of 
upper  base  ;  D  =  Diameter  of  lower  base) 

S  =  ^-   (D  +  d)  -h  -     (D2  +  d») 


Pyramid 

/  =  Slant  altitude 

p  =  Perimeter  of  base 

C  =  1/2  p  / 

S  =  1/2  p  /  +  area  of  base 

V  =  1/3  area  of  base  X  h 

137 


Frustum  of  a  Pyramid 

C  =  1/2  /  (P  +  P) 

S  =  1/2  (P  +  P)  /  +  A  +  a 

V=l/3h  (A -fa  4V  All) 

a  —  Area  of  upper  base 

A  =  Area  of  lower  base 

p  —  Perimeter  of  upper  base 

P  =  Perimeter  of  lower  base 

Centigrade  and  Fahrenheit  Scales 
Temperature 


Centigrade       Fahrenheit 

Centigrade       Fahrenheit 

0                     32 

50                        122 

5                      41 

55                       131 

10                     50 

60                       140 

15                     59 

65                       149 

20                     68 

70                       158 

25                     77 

75                       167 

30                     86 

80                       176 

35                     95 

85                       185 

38                     100.4 

90                       194 

40                      104 

95                       203 

42                      107.6 

100                       212 

45                     113 

Temp.  C  =  5/9 

(Temp.  F  —  32) 

Temp.  F  =  9/5 

(Temp.  C  +  32) 

138 


32.     Squares,  Cubes,   Square]  Roots, 
Cube  Roots  and  Reciprocals. 


No. 

Squires 

Cubes 

Square 
Roots 

Cube 
Roots 

Recip- 
rocals 

1 

1 

1 

1.0000 

1.0000 

1.0000 

2 

4 

8 

1.4142 

1.2599 

.5000 

3 

9 

27 

1.7320 

1  .4422 

.3333 

4 

»  16 

64 

2.0000 

1.5874 

.2500 

5 

25 

125 

2.2360 

1.7099 

.2000 

6 

36 

216 

2.4494 

1.8171 

.1666 

7 

49 

343 

2.6457 

1.9129 

.1428 

8 

64 

512 

2.8284 

2.0000 

.1250 

9 

81 

729 

3.0000 

2.0800 

.1111 

10 

100 

1000 

3.1622 

2.1544 

.1000 

11 

121 

1331 

3.3166 

2.2239 

.0909 

12 

144 

1728 

3.4641 

2.2894 

.0833 

13 

169 

2197 

36055 

2.3513 

.0769 

14 

196 

2744 

3.7416 

2.4101 

.0714 

15 

225 

3375 

3.8729 

2.4662 

.0666 

16 

256 

4096 

4.0000 

2.5198 

.0625 

17 

289 

4913 

4.1231 

2.5712 

.0588 

18 

324 

5832 

4.2426 

2.6207 

.0555 

19 

361 

6859 

4.3588 

2.6684 

.0526 

20 

400 

8000 

4.4721 

2.7144 

.0500 

21 

441 

9261 

4.5825 

2.7589 

.0476 

22 

484 

10648 

4.6904 

2.8020 

.0454 

23 

529 

12167 

4.7958 

2.8434 

.0434 

24 

576 

13824 

4.8989 

2.8844 

.0416 

25 

625 

15625 

5.0000 

2.9240 

.0400 

26 

676 

17576 

5.0990 

2.9624 

.0384 

27 

729 

19683 

5.1961 

3.0000 

.0370 

28 

784 

21952 

5.2915 

3.0365 

.0357 

29 

841 

24389 

5.3851 

3.0723 

.0344 

30 

900 

27000 

5.4772 

3.1072 

.0333 

31 

961 

29791 

5.5677 

3.1413 

.0322 

32 

1024 

32768 

5.6568 

3.1748 

.0312 

33 

1089 

35937 

5.7445 

3.2075 

.0303 

34 

1156 

39304 

5.8309 

3.2396 

.0294 

35 

1225 

42875 

5.9160 

3.2710 

.0285 

36 

1296 

46656 

6.0000 

3.3019 

.0277 

37 

1369 

50653 

6.0827 

3.3322 

.0270 

38 

1444 

54872 

6.1644 

3.3619 

.0263 

39 

1521 

59319 

6.2444 

3.3912 

.0256 

40 

1600 

64000 

6.3245 

3.4199 

.0250 

41 

1681 

68921 

6.4031 

3.4482 

.0243 

42 

1764 

74088 

6.4807 

3.4760 

.0238 

43 

1849 

79507 

6.5574 

3.5033 

.0232 

44 

1936 

85184 

6.6332 

3.5303 

.0227 

45 

2025 

91125 

6.7082 

3.5568 

.0222 

46 

2116 

97336 

6.7823 

3.5830 

.0217 

47 

2209 

103823 

6.8556 

3.6088 

.0212 

48 

2304 

110592 

6.9282 

3.6342 

.0208 

49 

2401 

117649 

7.0000 

3.6593 

.0204 

139 


32.    Squares,  Cubes,  Square  Roots,  Cube  Roots 

and  Reciprocals.— Continued. 


No. 

Squares 

Cubes 

Square 
Roots 

Cube 
Roots 

Recip- 
rocals 

50 

2500 

125000 

7.0710 

3.6840 

.0200 

51 

2601 

132651 

7.1414 

3.7084 

.0196 

52 

2704 

140608 

7.2111 

3.7325 

.0192 

53 

2809 

148877 

7.2801 

3.7562 

.0188 

54 

2916 

157464 

7.3484 

3.7797 

.0185 

55 

3025 

166375 

7.4161 

3.8029 

,  .0181 

56 

3136 

175616 

7.4S33 

3.S258 

.0178 

57 

3249 

185193 

7.5498 

3.8485 

.0175 

58 

3364 

195112 

7.6157 

3.8708 

.0172 

59 

3481 

205379 

7.6811 

3.8928 

.0169 

60 

3600 

216000 

7.7459 

3.9148 

.0166 

61 

3721 

226981 

7.8102 

3.9364 

.0163 

62 

3844 

238328 

7.S740 

3.9578 

.0161 

63 

3969 

250047 

7.9372 

3.9790 

.0158 

64 

4096 

262144 

8.0000 

4.0000 

.0156 

65 

4225 

274625 

8.0622 

4.0207 

.0153 

66 

4356 

287496 

8.1240 

4.0412 

.0151 

67 

4489 

300763 

8.1853 

4.0615 

.0149 

68 

4624 

314432 

8.2462 

4.0816 

.0147 

69 

4761 

328509 

8.3066 

4.1015 

.0144 

70 

4900 

343000 

8.3666 

4.1212 

.0142 

71 

5041 

357911 

8.4261 

4.1408 

.0140 

72 

5184 

373248 

8.4852 

4.1601 

.0138 

73 

5329 

389017 

8.5444 

4.1793 

.0136 

74 

5476 

405224 

8.6023 

4.1983 

.0135 

75 

5625 

421875 

8.6602 

4.2171 

.0133 

76 

5776 

438976 

8.7177 

4.2358 

.0131 

77 

5929 

456533 

8.7749 

4.2543 

.0129 

78 

6084 

474552 

8.8317 

4.2726 

.0128 

79 

6241 

493039 

8.8881 

4.2908 

.0126 

80 

6400 

512000 

8.9442 

4.3088 

.0125 

81 

6561 

531441 

9.0000 

4.3267 

.0123 

82 

6724 

551368 

9.0553 

4.3444 

.0121 

83 

6889 

571787 

9.1104 

4.3620 

.0120 

84 

7056 

592704 

9.1651 

4.3795 

.0119 

85 

7225 

614125 

9.2195 

4.3968 

.0117 

86 

7396 

636056 

9.2736 

4.4140 

.0116 

87 

7569 

658503 

9.3273 

4.4310 

.0114 

88 

7744 

681472 

9.  -808 

4.4479 

.0113 

89 

7921 

704969 

9.4339 

4.4647 

.0112 

90 

8100 

729000 

9.4868 

4.4814 

.0111 

91 

8281 

753571 

9.5393 

4.4979 

.0109 

92 

8464 

778688 

9.5916 

4.5143 

.0108 

93 

8649 

804357 

9.6436 

4.5306 

.0107 

94 

8836 

830584 

9.6953 

4.5468 

.0106 

95 

9025 

857375 

9.7467 

4.5629 

.0105 

96 

9216 

884736 

9.7975 

4.5788 

.0104 

97 

9409 

912673 

9.8488 

4.5947 

.0103 

98 

9604 

941192 

9.8994 

4.6104 

.0102 

99 

9801 

970299 

9.9498 

4.6260 

.0101 

100 

10000 

1000000 

10.0000 

4.6415 

.0100 

140 


Rates 

The  cost  of^'generating  and  delivering  elec- 
trical energy  may  be  considered  as  divided  into 
two  parts, — running  expenses  and  standing  ex- 
penses :  The  running  expenses  comprise  the  cost 
of  fuel,  labor,  repairs,  supplies  and  water,  and 
are  proportional  to  the  power  used.  The  stand- 
ing expenses  consist  of  depreciation,  interest 
and  general  expenses.  The  standing  expenses 
may  be  regarded  as  fixed,  yet  they  are  de- 
pendent on  the  character  of  the  load,  or  rather 
on  the  load  factor.  From  60  to  70  per  cent,  of  the 
entire  expense  is  represented  by  the  standing 
expense  so  that  the  rate  charge  per  kw-hr.  will 
increase  rapidly  when  conditions  demand  a  high 
standing  expense. 

In  adjusting  rate  schedules  the  following  fac- 
tors demand  first  consideration: —  The  con- 
sumer's "demand"  on  the  capacity  of  his  install- 
ation or  connected  load  for  drawing  on  the 
station;  the  number  of  hours  use  to  which  he 
puts  his  capacity;  the  "interweave"  or  variation 
in  the  consumer's  use  of  service;  the  cost  of  gen- 
erating the  current  itself.  In  any  receiving  in- 
stallation it  is  probable  that  the  consumer's  de- 
mand will  seldom  reach  the  maximum  of  his 
installed  capacity,  yet  when  it  does  he  wishes 
good  service,  and  the  central  station  must  be 
able  to  supply  it.  Again,  when  the  demand  of 
any  one  class  of  consumers  is  highest  the  de- 
mand of  the  other  consumers  will  probably  be 
low.  The  aggregate  of  these  variations  is  called 
the  "interweave."  If  it  were  not  for  this  inter- 
weave the  central  station  would  need  equipment 
enough  to  meet  the  simultaneous  demand  of  the 
total  connected  load  on  its  lines.  This  would 
require  a  large  investment  in  machinery  equip- 
ment and  help,  -syhich  would  necessarily  be  idle 
and  non-productive  at  times.  There  are  varia- 
tions in  interweaves,  however,  for  different 
hours  of  the  day  and  different  seasons  of  the 
year,  and  the  central  station  must  be  equipped 
to  meet  the  maximum  demand  for  the  inter- 
weave. On  this  account  the  customer  with  a 
large  installed  capacity  connected  to  the  linevS 
represents  a  standing  expense  to  the  station, 
irrespective  of  his  use  of  current,  and  rates 
should  be  adjusted  with  this  in  mind. 

The  customer  who  uses  his  installation  a  large 
number  of  hours  per  day  is  more  profitable  to 
to  the  central  station  than  the  customer  who 
uses  a  large  amount  of  current  for  only  a  few 
hours.  This  is  due  to  the  fact  that  the  portion 
of  maximum  demand  on  the  central  station  that 
may  be  considered  as  reserved  for  this  customer 
is  producing  returns  in  revenue  for  a  greater 
number  of  hours,  or,  stating  it  in  other  terms, 
the  equipment  reserved  for  this  customer  is  idle 

141 


a  smaller  number  of  hours,  accordingly  the  loss 
due  to  investment  on  non-productive  equip- 
ment is  lowered. 

The  factors  in  rate  adjusting-  vary  to  a  great 
extent  for  different  classes  of  service,  and  it  is 
difficult  to  use  any  one  schedule  without  appar- 
ent discrimination,  favorable  or  unfavorable  to 
some  one  of  the  different  classes.  In  general, 
however,  the  object  should  be  to  charge  for  the 
service  in  direct  proportion  to  the  cost  of  serving. 

Rate  Schedules 


Flat  Rates 

,    A  fixed  rate  per  kilowatt  hour.    This  system 
does  hot  provide  a  fair  return  to  the  company, 
neither    does    it    encourage  the  profitable  cus- 
tomer. 
Rate  Differentials 

A  lower  rate  is  given  for  motors  and  battery 
charging  than  for  lighting  loads.  This  is  ad- 
visable when  these  two  classes  of  service  are 
limited  to  the  hours  when  otherwise  a  part  of 
the  equipment  would  be  idle,  although  some 
classes  of  motor  load,  as  elevators,  etc.,  by  their 
intermittent  service,  may  seriously  affect  the 
lighting  voltage. 
Manchester  or  Hopkinson  System 

A  fixed  price  is  charged  for  each  kilowatt  of 
installed  capacity,  plus  the  price  per  kilowatt 
hour.  The  chief  objection  to  this  system  is  that 
it  discourages  the  installation  of  lamps  excepting 
where  they  are  burned  for  long  hours,  or  where 
they  are  considered  a  necessity.  It  also  tends  to 
make  the  cost  of  residential  lighting  unattractive. 
Rate  Discounts 

A  discount  is  given  on  the  gross  bills  and  also 
an  additional  discount  based  on  the  average  use 
of  the  installation.  The  objection  to  this  system 
is  that  the  discount  rate  must  evidently  be  di- 
vided into  steps.  In  case  of  a  5%  discount  on  a 
$100  bill  the  charge  would  be  $95,  while  a  bill  for 
$98  would  not  be  discounted,  so  that  the  first  cus- 
tomer would  get  more  energy  for  $95  than  the 
second  would  get  for  $98. 
Wright  or  Brighton  Demand  System 

In  this  system  the  customer  pays  his  equitable 
quota  of  the  strictly  fixed  charges  and  also  of 
the  standby  charges.  These  items  are  included 
in  the  charge  per  hour  made  for  the  first  hour's 
use  of  the  number  of  lamps  equivalent  to 
practically  the  maximum  number  of  lamps  used 
at  any  one  time.  For  the  energy  used  in  ex- 
cess of  the  first  hour's  average  use  of  the  maxi- 
mum demand  the  customer  pays  a  different  rate 
proportional  to  the  additional  expense  which  the 
company  is  under  in  supplying  him  with  ad- 
ditional energy, 

142 


Kapp  System 

The  rate  is  based  on  the  time  of  maximum  de- 
mand of  the  consumer  as  compared  with  the 
time  of  the  station's  maximum  load.  The  ad- 
vantage of  this  system  is  that  the  customer, 
who  for  the  same  total  current  supplied  to  him 
contributes  least  to  the  station's  maximum  load, 
benefits  most  largely  by  discounts. 

Wholesale  or  Bulk  Supply 

Energy  is  usually  sold  under  a  flat  rate  and  at 
a  reduced  price.  The  reduction  is  due  partly 
to  the  fact  that  a  large  supply  can  be  furnished 
more  cheaply  per  unit  than  a  smaller  supply. 
The  chief  reason  for  lowering  the  rate,  how- 
ever, is  that  this  class  of  business  is  usually  com- 
petitive and  a  lower  rate  must  be  given  to  obtain 
the  contract. 


143 


Resuscitation  From  Electric  Shock 

FOLLOW   THESE    INSTRUCTIONS    EVEN    IF 
VICTIM  APPEARS  DEAD 

/.    Immediately  break  the  circuit. 

With  a  single  quick  motion,  free  the  victim 
from  the  current.  Use  any  dry  non-conductor 
(clothing,  rope,  board)  to  move  either  the  victim 
or  the  wire.  Beware  of  using  metal  or  any  moist 
material.  While  freeing  the  victim  from  the  live 
conductor  have  every  effort  also  made  to  shut 
off  the  current  quickly. 
//.  Instantly  attend  to  the  victim's  breathing. 

1.  As  soon  as  the  victim  is  clear  of  the  con- 
ductor, rapidly    feel   with    your    finger   in    his 
mouth  and  throat  and  remove  any  foreign  body 
(tobacco,  false  teeth,  etc. ) .    Then  begin  artificial 
respiration  at  once.     Do  not  stop  to  loosen  the 
victim's  clothing  now;  every  moment  of  delay  is 
serious.    Proceed  as  follows: 

(a)  Lay  the  subject  on  his  belly,  with  arms 
extended  as    straightforward    as    possible    and 
with  face  to  one  side,  so  that  nose  and  mouth 
are  free  for  breathing.     Let  an  assistant  draw 
forward  the  subject's  tongue. 

(b)  Kneel  straddling  the  subject's  thighs  and 
facing  his  head;  rest  the  palms  of  your  hands  on 
the  loins   (on  the  muscles  of  the  small  of  the 
back),  with  fingers  spread  over  the  lowest  ribs. 

(c)  With  arms  held  straight,  swing  forward 
slowly  so  that  the  weight  of  your  body  is  grad- 
ually, but  not  violently,  brought  to  bear  upon 
the  subject.    This  act  should  take  from  two  to, 
three  seconds. 

Immediately  swing  backward  so  as  to  remove- 
the  pressure,  thus  returning  to  the  first  position. 

(d)  *  Repeat  deliberately  twelve  to  fifteen  times 
a  minute  the  swinging  forward    and    back-  a 
complete  respiration  in  four  or  five  seconds. 

(e)  As  soon  as  this  artificial  respiration  has 
been  started,  and  while  it  is  being  continued,  an 
assistant  should  loosen  any  tight  clothing  about 
the  subject's  neck,  chest  or  waist. 

2.  Continue  the  artificial  respiration  (if  neces- 
sary, at  least  an  hour),  without  interruption, 
until  natural  breathing  is  restored,  or  until  a 
physician  arrives.    If  natural  breathing   stops 
after    being  restored,  use  artificial  respiration 
again. 

3.  Do  not  give  any  liquid  by  mouth  until  the 
subject  is  fully  conscious. 

///.    Send  for  nearest  doctor  as  soon  as  accident 

is  discovered. 

A  poster  embodying  the  above  rules  hag  been  published  and 
distributed  by  the  ELECTRICAL  WORLD. 


INDEX 


A 

Ampere 1 

Automobile  Lighting 35 

B 
Batteries 

Storage 118 

Lead  Plate 118 

Edison 121 

Bunsen  Screen 7 

C 

Calculation  of  Illumination 12 

Candle-power 1 

Mean  Horizontal 2 

Mean  Spherical 2 

Mean  Zonular 2 

Circle 136 

Circular  mil 2 

Circular  ring 137 

Cleaning  Mazda  Lamps 63 

Constants,  illumination 19 

Cone 137 

Connections,  transformers 128 

Cost  of  light  formula 74 

Cube  root 133 

Curves,  distribution 31 

Cylinder 137 

D 

Differential  rate 142 

Distribution  curves 31 

Distribution  systems 93 

E 

Edison  battery 121 

Electrical  units 1 

Ellipse 136 

P 

Fechner's  fraction 1 

Fixtures 82 

Flat  rates 142 

Flux  of  illumination 1 

Foot  candles 12 

Formulae  used  in  calculation  of  lamp  data...      5 
Frustum 

of  a  cone 137 

of  a  pyramid 138 

Glare 1 

H 
Hopkinson  System 142 

Illumination 1 

calculation  of 12 

fundamental  formula 12 

constants 19 

Ml 


I 

Intensities  recommended 23 

Intrinsic  brilliancy 1 

K 

Kapp  System 143 

Kilowatt 2 

L 

Lambert's  Law 17 

Lamps 

Automobile 35 

Gem,  advantages  of 66 

Miniature 35 

Low  voltage 35 

Mazda 65 

Sign 40 

Street  series 50 

Train 38 

Law  of  Inverse  Squares 12 

Lead  plate  battery US 

Leeson  Disc 7 

Lighting 

Mills 53 

Sign 40 

Street 50 

Losses  in  incandescent  filaments 80 

Lumen 2 

Lumen  constant 19 

Lummer  Brodhun  screen 7 

M 

Manchester  System 142 

Mazda  lamps 65 

Cleaning 63 

Energy  losses 80 

Mensuration 133 

Mercury  arc  rectifier 101 

Mill  lighting 53 

Miniature  lamps 35 

N 
National  Electric  Code 110 

O 

Ohm 2 

Ohm's  Law 3 

P 

Parallelogram 136 

Photometry 6 

Point  by  point  method 13 

Purkinje  effect 2 

Pyramid 137 

R 

Rate  schedules 142 

Rectangle 136 

Rectifier  .mercury  arc 101 

Reflectors,  types  and  styles  of •••    28 

S 
Schedules,  rate 142 

ux 


s 

Sector • 136 

Segment 1--7 

Sign  lighting... 40 

Sphere • 137 

Spacing  of  units 21 

Square  root 133 

Street  lighting 50 

Systems  of  distribution 93 

T 

Transformers 123 

Types 123 

Core  loss 123 

Hysteresis  loss ••  123 

Foucault,  Eddy  current  loss 123 

Copper  loss 123 

Efficiency 123 

Regulation 124 

Testing 124 

Connections 128 

Installation 129 

Operation 129 

Train  lighting 38 

Trapezium 136 

Trapezoid 136 

Triangle 136 

V 

Visual  acuity 3 

Volt 3 

W 

Watt 3 

Watt-hour 3 

Wire  data 104 

Wiring  Symbols 116 

Wright  System 142 


General  Electric  Company 

>>r!  iciuRl  Offices,  S-henectady,  N.  Y. 

'  \     ;     General  Sale**  Office 
Edison  Lamp  Department, 
Harrison,  N.  J. 

SALES  OFFICES 
(Address  nearest  »ffice) 

BOSTON.  MASS 84  State  Street 

Springfield,  Mass Massachusetts  Mutual  Building 

Providence,  R.  I Union  Trust  Building 

NEW  YORK,  N.  Y 30  Church  Street 

Rochester,  N.  Y Granite  Building 

Syracuse,  N.  Y Post-Standard  Building 

Buffalo.  N.  Y Ellicott  Square  Building 

Erie,  Pa Marine  National  Bank  Building 

New  Haven,  Conn Malley  Building 

PHILADELPHIA,  PA Witherspoon  Building 

Baltimore,  Md Electrical  Building 

Charlotte,  N.  C Trust  Building 

Charleston,  W.  Va Charleston  National  Bank  Building 

Pittsburgh,  Pa Oliver  Building 

Richmond,  Va Mutual  Building 

Youngstown,  Ohio Wick  Building 

ATLANTA,  GA Third  National  Bank  Building 

Birmingham,  Ala Brown-Marx  Building 

New  Orleans,  La Maison- Blanche  Building 

Jacksonville,    Florida Florida  Life  Building 

CINCINNATI,  OHIO Provident  Bank  Building 

Columbus,  Ohio Columbus  Savings  &  Trust  Building 

Cleveland,  Ohio Citizens  Building 

Dayton,  Ohio Reibold  Building 

Toledo,    Ohio Spitger  Building 

Chattanooga,  Tenn James  Building 

Knoxville,  Tenn Bank  and  Trust  Building 

Memphis,  Tenn Randolph  Building 

Nashville,   Tenn Stahlman  Building 

Indianapolis,  Ind Traction  Terminal  Building 

Louisville,  Ky Paul  Jones  Building 

CHICAGO,  ILL Monadnock  Building 

Davenport,  Iowa Security  Building 

Keokuk,  Iowa Monarch  Building 

Detroit,  Mich Majestic  Building  (Office  of  Soliciting  Agent) 

Joplin,  Mo Miners'  Bank  Building 

St.  Louis.  Mo Wairtwright  Building 

Kansas  City,  Mo Dwight  Building 

Butte,  Montana Electric  Building 

Minneapolis,  Minn 410  Third  Ave.,  North 

Milwaukee,  Wis Public  Service  Building 

DENVER,  COLO First  National  Bank  Building 

Boise,  Idaho Idaho  Building 

Salt  Lake  City,  Utah Newhouse  Building 

SAN  FRANCISCO,  CAL Rialto  Building 

Los  Angeles,  Cal 124  West  Fourth  Street 

Portland.   Ore Electric  Building 

Seattle,  Wash Colman  Building 

Spokane,  Wash Paulsen  Building 

For  TEXAS  and  OKLAHOMA  Business  refer  to 
Hobson  Electric  Company 

Dallas,  Tex Lamar  &  Caruth  Streets 

El  Paso,  Tex Chamber  of  Commerce  Building 

Houston,  Tex Chronicle  Building 

Oklahoma  City,  Okla Insurance  Building 


FOREIGN  SALES  OFFICES 
Schenectady,  N.  Y. ,  Foreign  Dept. 
New  York,  N.  Y.,  30  Church  St. 
London,  £.  C.,  England,  83  Caonon  St. 

For  all  CANADIAN  Business  refer  to 

Canadian  General  Electric  Co,,  Ltd,,  Toronto,  Oat, 


Additional  Data 


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